# Schwinn Serial Number Stamping



## Metacortex

Referencing this topic showing an upside-down serial number stamp (and I've seen and heard of several others http://thecabe.com/forum/threads/someone-please-explain-this-photo-for-me.85709/

I just acquired the May 1978 Schwinn Reporter filling in a gap in my collection and finally have located definitive documentation about how and when the serial numbers were stamped in the frame manufacturing process:









As the article states the serial number was stamped as part of the very last operation in the headtube manufacturing process (along with drilling the badge holes). Considering the shape of the headtube and the stamping process you can see how easy it would have been to stamp some upside-down.

Thinking about this further, I've never seen or heard of a fillet-brazed bike with an upside-down serial number. The fillet-brazed bikes would have had this stamping and drilling done on a bare tube with no protrusions (meaning no up from down other than the serial number location). Since in that case the serial number would be the only indication of up or down and since they were subsequently hand-brazed it is no wonder you never see a fillet-brazed bike with an upside-down serial number. Comments anyone?


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## GTs58

Very interesting. I was close, real close.  :=)


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## Schwinn499

I saw those reporters in the sold listings...I had a feeling it was you. Thanks for sharing. Cool stuff right there. Schwinn bikes are the best!


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## Dale Alan

That is great info,good to see the facts . Thanks for sharing.


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## momo608

Great stuff! 

I hope you make a habit of putting these articles up.

So much for my theory of stamping while a flat plate.

No scanner? I had to zoom in quite a bit to read some of it. Our friends with small screens might not be able to read it.


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## Jeff54

Just about how I expected reverse, up-side-down serial numbers got there. Cept, I hadn't imagined it would have been done before the whole frame was assembled.

That is, I wouldn't put numbers on a part, alone, until it reached the last stage of whole assembly, Quality control inspection and serial number stamp, before painting. Because, the number would be lost if any error occurred before completed.


So, good ol'Hangover Mondays', Jamie Marquet did it!


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## Metacortex

According to other Schwinn documents when the serial numbers were on the LH rear dropout, those dropouts were also serial number stamped before being welded into the frame. That is also why in early 1970 when Schwinn moved the serial numbers from the dropout to the headtube there were some frames built with serial numbers in *both* places, and the numbers did not match.

In the case of the headtube manufacturing process you can now see why the number was stamped last, if it had been stamped on one of the flat plates at the beginning of the process it probably wouldn't have survived the pressing, welding, scarfing, grinding, sizing and polishing that followed.

Here is a pic I found online that shows one of the headtube halves being stamped in a press:





Unfortunately I don't have access to a scanner right now but I did make sure the full-page pic was sized so the text was readable zoomed in, and that's what counts.


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## Jeff54

Metacortex said:


> Here is a pic I found online that shows one of the headtube halves being stamped in a press:
> 
> .




Well that photo also splains why they'd gone on strike and virtually killed Schwinn's business. The strike must have been an attempt to abolish their slave trading business too. [grin]


Alternatively, I'd guess that chain and wrist band pulls the worker's hand clear of the press. 'Hang-over Mondays' safety prevention


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## GTs58

Some food for thought on this subject. I'm still believing the SN's were stamped flat, at least for 1970 when all these upside down and wrong side stampings occurred. The serial number location was changed to the head tube in early 1970 and prior to that all the stampings were done on flat steal. So it's very possible Schwinn started stamping the head tube numbers while it was flat since their original equipment was for stamping serial numbers on flat steel. This Reporter was from 1978, so when "exactly" did Schwinn install this new serial number stamping equipment for round tubing? Anyone ever see the reversed stamping on a head tube later than 1970? Any news in the Reporters saying when Schwinn upgraded their stamping equipment?


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## momo608

GTs58 said:


> Some food for thought on this subject. I'm still believing the SN's were stamped flat, at least for 1970 when all these upside down and wrong side stampings occurred. The serial number location was changed to the head tube in early 1970 and prior to that all the stampings were done on flat steal. So it's very possible Schwinn started stamping the head tube numbers while it was flat since their original equipment was for stamping serial numbers on flat steel. This Reporter was from 1978, so when "exactly" did Schwinn install this new serial number stamping equipment for round tubing? Anyone ever see the reversed stamping on a head tube later than 1970? Any news in the Reporters saying when Schwinn upgraded their stamping equipment?




I thought a clue to the head tube being serial number stamped flat is that the serial numbers are on one side of the tube. Not going past the welded butt joint.


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## GTs58

momo608 said:


> I thought a clue to the head tube being serial number stamped flat is that the serial numbers are on one side of the tube. Not going past the welded butt joint.




Another good point. So now the question is, when did the SN's first get stamped with this equipment in the 78 Reporter?


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## Metacortex

GTs58 said:


> Anyone ever see the reversed stamping on a head tube later than 1970?




I have: http://www.bikeforums.net/classic-vintage/798805-rare-schwinn-error-serial.html 



GTs58 said:


> ...when did the SN's first get stamped with this equipment in the 78 Reporter?




We know that headtube serials started in early to mid 1970. The article I pictured states that "frame heads are fabricated at Plant #4, Schwinn's newest facility, devoted exclusively to producing frames. In full operation by 1974." So it could have been functioning even earlier than that, and there is little reason to suspect they changed how headtubes were made.



momo608 said:


> I thought a clue to the head tube being serial number stamped flat is that the serial numbers are on one side of the tube. Not going past the welded butt joint.




They did sometimes go up to and even past the welded butt joint:






OK guys, did you read the article I posted?  Again there is no way the serial would have survived on the headtube legibly after the pressing, welding, scarfing, grinding, sizing and polishing that happened after the flat plates were stamped.


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## GTs58

Weren't there many parts of the Tandem frame that were not EF and was filet brazed? Here is that same 1970 twinn that was double stamped with a SN.





I've also seen non EF head tubes on the road bikes where the serial number is near or centered in the head tube. Read all the reporter last night.
I work for a company that does light manufacturing and I use a grinder and flap sander on a daily basis. The head tube halves are rolled with high pressure stamps and it's not like they were hammered round so I see no good reason why a serial number would not survive a flash weld, grinding and polishing on sliver of metal slag in a single small area or the rolling by stamping equipment.

Can someone copy and paste that picture of the 1980 Cruiser from that other forum? I'm not going to join another forum just to look at one picture. Thanks!


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## Schwinn499

I think the font and size of the text changed with the change in placement as well. So probably not the same stamping equipment. Id have to go with Metacortex on this one, serials were almost certainly stamped as said in the reporter the entire run of these serials.


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## momo608

I'm sold, I already gave up on my theory after reading the Reporter.

For whatever it's worth the Chrome Moly filet brazed frames are number stamped differently. Many times the stamping is so light you can hardly see it.


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## Metacortex

GTs58 said:


> Weren't there many parts of the Tandem frame that were not EF and was filet brazed?




That is correct, so not the best example in this case. Here is another much better example, taken from a '72 Varsity seen here: http://www.bikeforums.net/classic-v...ity-sport-chrome-fenders-worth-restoring.html





While that serial isn't centered, it definitely crosses into the welded area between the headtube halves.



> Can someone copy and paste that picture of the 1980 Cruiser from that other forum?


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## Metacortex

momo608 said:


> For whatever it's worth the Chrome Moly filet brazed frames are number stamped differently. Many times the stamping is so light you can hardly see it.




I have seen some with lighter stamps, but that isn't the rule. These look pretty much the same to me:

1972 Varsity:




1971 Sports Tourer:


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## Jeff54

Metacortex said:


> That is correct, so not the best example in this case. Here is another much better example, taken from a '72 Varsity seen here: http://www.bikeforums.net/classic-v...ity-sport-chrome-fenders-worth-restoring.html




There is a difference in the numbers by 1980. your green above is bold and is pressed so hard it pushes the post in, the other green previously has a slight bend too.  While later, it's lighter, sloppier and perhaps a slightly different font. Sloppiest, in that blue upside-down set  too. Either they've used the number press so much it's out, or an entirely different stamping mechanism.

This is 1980 Cruiser and the set is not close to front center.


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## Metacortex

Jeff54 said:


> There is a difference in the numbers by 1980...




I don't think you can ascribe that to a given year or a specific change over time. I'd say the stamps were affected more by the operator and machine settings, combined with wear on the dies. Given they stamped more than a million bikes some years I'd imagine the dies would have to be changed from time to time. For example here is a '73 Continental with a very light stamp:


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## cds2323

And here is a 1980 Cruiser 5 with a bolder stamp than the one posted by jeff54. (Edit: not sure why but I misread the serial number on jeff54s bike as BR not HR, still a deeper stamping). Not far apart either.


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## momo608

Luck of the draw, my two Sports Tourer's 72 and 73 frames and 76 Superior frame look as bad or worse than that black 80 cruiser. They will undoubtedly be almost invisible after a base coat clear coat paint job. The 73 already is. I picked out the serial numbers with a needle just to be sure that they were absolutely clean before the paint went on. Primer, sealer, several base coats and then the clear, they did not have a chance.


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## Jeff54

Metacortex said:


> I don't think you can ascribe that to a given year or a specific change over time. I'd say the stamps were affected more by the operator and machine settings, combined with wear on the dies. Given they stamped more than a million bikes some years I'd imagine the dies would have to be changed from time to time. For example here is a '73 Continental with a very light stamp:





Yeah, it was that up-side-down blue 80's cruiser that kicked me off, as its stamp sucks in all directions! [grin] , and my 80 black seems not to swell, but, I looked at others too. This set on a late 80 frame 1981 build, and it's tight..

Come to tink on it, I'm tinkin now, that, errors in such things devalues a collectible as, peps like accuracy as much as best original paint too. I mean, like, if they'd put decals on a bike as crappy as some numbers were, who'd pick that 1st? ? Who's Choice bike was built on 'Hangover Monday', and loves it? [grin]

BTW CDS, your's is an MR, my black is an HR, and so, this below, truly really is 'close' in time.. just 1,705 lower, like, within a day or so. An me bets that your build date, on your badge, is 81 too.

Regardless we're getting side tracked, while that brown set Metacortex posted today   raps the subject tight, like earlier, the green, there's no way they'd been stamped on flat pre-molded metal.


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## Metacortex

Somebody who is an SBF member should point them over here for more accurate information  http://www.schwinnbikeforum.com/index.php?topic=33816.0


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## GTs58

All I'm seeing from the link is this.


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## Intense One

1975 Speedster with stamp off centered as well


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## Metacortex

Intense One said:


> View attachment 287882 1975 Speedster with stamp off centered as well




From the pic it looks like the serial number starts with "LJ", which dates the frame (or at least the head tube) to Nov. 1973. However the bike is painted Opaque Red (a 1974 only color), which means it wasn't painted and built into a bike until early in 1974. That of course makes it a '74 model, here is the catalog page for that year:


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## jnewkirk77

Here's the SN from my new '76 Continental ... I thought it was a little odd that the CM isn't lined up with the numbers. They sure nailed that "3" in there good, though. :eek:


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## Intense One

Metacortex said:


> From the pic it looks like the serial number starts with "LJ", which dates the frame (or at least the head tube) to Nov. 1973. However the bike is painted Opaque Red (a 1974 only color), which means it wasn't painted and built into a bike until early in 1974. That of course makes it a '74 model, here is the catalog page for that year:





Metacortex said:


> From the pic it looks like the serial number starts with "LJ", which dates the frame (or at least the head tube) to Nov. 1973. However the bike is painted Opaque Red (a 1974 only color), which means it wasn't painted and built into a bike until early in 1974. That of course makes it a '74 model, here is the catalog page for that year:



Agreed, Metacortex...the Speedster is a '74 model built late '73 in one year only Opaque red.  I have a stingray with JK stamp also a '74 model built in Sept. '74 and in one year availability opaque red too


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