Hi jerry, and Rodger.
Again, I would like to say 'Thanks' for letting us see this bicycle in detail.
Here are some random thoughts in a haphazard order about this bike. They are my own opinion, and I'm happy to discuss them to try to get a correct idea of the history of this bicycle.
It is the first non-G519 I've seen with the date stamped on the bb. As far as I can tell so far, only Huffman bikes accepted into Military service had the date stamped on them, civilian ones didn't, so I'm inclined to think that it is more likely to be part of a small order than a prototype. Jerry has mentioned that he knows of one other. We also know that orders under $50,000 weren't published, and you could easily have bought 1000 bikes of this type for less than that. We also know the survival rate for known G519's at the moment is about 1 in a 1000, so just a handful of survivors wouldn't be a surprise.
Some pictures exist of the USMC using these Victory Lightweight style frames, and I always assumed they were the civilian pattern bought in, but I'll need to go back and look to see if there are truss rods visible on them. It's possible that the USMC ordered these as Military specification bikes, and then just bought the civilian ones 'off the shelf' so that there were no problems with waiting for them to be produced due to the variation in specification between these and the Victory Lightweights.
The serial numbers were applied after the frame was painted, which is why they've rusted. That's normal for Huffman bikes at this point, and tells us that it is the original paint for the frame.
I think (though I could be wrong) that the numbers on the rear of the fork are 13, indicating it was made in January 1943. Below is a picture of a January 1944 fork with 14 stamped on it. Huffman used a strange stamp set on these, and you can see how much bigger the 1 is than the 4 (which are the only two conceivable first numbers on the USMC fork), so I think it's a 1, simply from style. It's not overly important (though I'd love to know for sure), since 43 would be April 1943, the M1 on the Morrow is Q1 1943, the frame number, in comparison to other known ones, would be late 1942, early 1943, except that it is stamped 1943, so again, early 1943.
Picture credit : okozzy
The truss rods with the separate support at the mudguard comes from G519 production. This was probably the first Huffman production bike to use this style. Westfield always used this style of bracket on G519's, though the rods were slightly different, as were the bolts on the top holding them on. It can be seen in one of Jerry's photos that the recessed Huffman bolts have been used. Some further detail here:
https://thecabe.com/forum/threads/inside-threaded-truss-rods.169945/page-2#post-1156450 Huffman used supports welded directly to the fork for most, if not all of their first G519 contract. This Westfield format was adopted for their second G519 contract, and the USMC bike sits between the two, so is an early Huffman example of this.
The front hub is marked Eclipse 36-10, which is the same heavy gauge hub as used on G519, so I've no doubt the rear is marked in the same way. Because they are Army green, they appear to have been drawn from G519 stock.
Westfield produced G519 stuck quite rigidly to specification for parts. Huffman, as a smaller supplier, seem to have had to substitute parts for their G519's more often, and known variations from the Westfield version which were not manufacturer specific include seats, wheel rims, pedals, grips.
Huffman used at least two wheel rim types on G519, but not this one. At the very end of G519 production (very late 1943 to early 1944) , Westfield used these rims when they produced a small batch, or possibly two, of bicycles that were similar to the Army G519, but marked MC rather than MG for the serial number,. It's generally accepted (though there is still no absolute proof) that these are USMC contract bikes. They have similarities to this one, such as the 'hooked' wheel rims, the drop stand, the colour.
The pedals are by Persons, and have been seen on production Huffman G519, though there has been controversy as to whether they were original (I personally think so), or substitute spares from stores. The link is to a unrestored Huffman with the same pedals, and a Mesinger saddle too. I don't know if the hex head bolts through the blocks on the pedals are replacements, or again, substitute standard, since they don't match the round headed bolts more commonly seen. This G519 dates to July/August 1943.
https://forums.g503.com/viewtopic.php?t=229295
Another slightly esoteric feature of this bike is that it has a Huffman headbadge. By this point of the war, civilian models didn't have them (indeed, that's why Huffman started stamping H in front of the serial number, Westfield did the same with civilian bikes receiving a W), G519 bikes always had headbadges, as does this bike, which implies military again. As an example, here is a similar dated (2 or 3 weeks earlier than the USMC bike), but civilian Huffman without a headbadge, or even screwholes for one. I've just noticed it has Persons pedals too, though I'm not sure if the blocks are wood or rubber.
https://thecabe.com/forum/threads/blackout-huffman-bike-greasy-too.147805/
Paint, as Jerry observed, anything from the G519 parts bin is in an Army green, otherwise USMC.
As I said, feel free to add comments, and I'm very happy to discuss any of the observations above, or respond to any particular questions (I can't guarantee I'll know the answer). (-:
Best Regards,
Adrian