Miq, Thanks for putting a time-line together. I hadn't thought about it but it makes sense that the restrictions weren't imposed all at once. Hindsight is 20/20, but going forward you have to adjust as the situation develops, and there's no way they could know what we know now. Nice work!
Thanks
@Oilit ! Crawling through the stacks of Federal Register PDFs at the fedgov.gov is kind of painful. I can see why no one other than
@HUFFMANBILL has been combing it. I took a deeper dive this morning. The past few posts have been really old document intensive. I will try to condense this stuff down as much as possible, but this is still going to be dense without any bike pics

:
The Federal Register published an
annual index every year. These are searchable for keywords once you download them as a PDF. Here are the War Production Board entries from 1942 for "Bicycles and bicycle parts"
These identify what page to look for these War Production Board entries in the Federal Registries published throughout the year.
Page 1980 is the Initial Limitation Order L-52 from the
March,13 1942 issue:
Two periods set up with up to 47lb bike manufacturing and sales for 20 days, and further restrictions like 31 lb weight limit, diamond frames and no chainguards/kickstands starting in April.
Page 2696 the Order starts to be modified, pretty quickly in the
April, 4 1942 issue.
Looks like after the first 20 days, they decided there would be a pause on selling and delivering adult bikes.
Page 2679 the frame size restriction is changed to allow a shorter 17" seat tube dimension.
April 8. 1942 issue:
This was the original 19" call out that was changed:
Page 3547 from the
May 14, 1942 issue has an interesting call out:
It is now allowed to sell bicycles to people with Office of Price Administration certificates. We have seen a few Part C final copies of these certificates, here's one from June 1943 for a K serial New World:
and
@dogdart 's J serial Sept. 1942 New World certificate with envelope with hand written note from the original owner saying her New World was called a "Victory Bike"

:
Page 5509 in the
July 18,1942 issue:
This one does some updating and refining of the Limitation order. Now that it is July, the second half of the year restrictions are getting clear and the rules from the past few months get extended.
Subparagraph b4 is the section on the restrictions called out as the 3 months ending in June. This makes it clear that these restrictions (less than 31 lbs, diamond frame, 17" Seat tube, etc.) are in effect from April 1 onward.
Subparagraph b5 is the section for Parts Manufacturers and it also gets changed to be effective for every three months after the initial 3 months ending June 30th.
New subparagraphs (7 & 8) are added at the end of the Limitation Order. These call out the quantity of bicycles a manufacturer could be allowed to manufacture from July 1 to Aug 31. During July and Aug 1942 the quantity of bikes built had to be less than 2 times 32% of the Average Monthy Manufacturing Quantity from 1941.
Paragraph 8 calls out the end of production work on any bicycle related stuff effective Sept 1, 1942. This sets the stage for the final change in Sept.
Page 6934 Federal Register
Sept. 2, 1942 issue:
This is the Second Amendment and we have already seen that this was the call out to Huffman and Westfield to build Victory Bikes. We also know from the Advertisments in Amercian Bicyclist and Motorcyclist that Schwinn had petitioned to also get approval (that was granted) to build victory bikes. The centerfold Ad for the New World War VW1M Model came from the March 1942 Issue:
And also in the September issue, around the time the Second Amendment was published in the Fed Register listing Huffman and Westfield as the only allowed bike manufacturers.
Defense and Wartime Bicycle Timeline
Oct 1941 - Schwinn reports that the use of Chrome and Nickel will be limited on their bikes.
Dec 1941 - Pearl Harbor - US Enters WWII
Early 1942 ? - Defense Models are Announced
March 1942 American Bicyclist Magazine Centerfold Ad for New World War Model VW1M
March 11, 1942 - War Production Board Limitation L-52 Issued (Page 1980 Fed Register March 13 issue)
March 11 - March 31, 1942 - Restricted Period with 47 lb weight limit
April 1 1942 and onward - Second Limitation Period with 31 lb weight, diamond geometry, and accessories restrictions.
May 14, 1942 - OPA Certificates Allowed (Page 3547 Fed Register May 14 issue)
July 18, 1942 - War Prod. Board L-52 First Ammendment - July and Aug quantity limits, Sept No More Bike Manufacturing. (Page 5509 Fed Reg July 18 issue)
September 1942 American Bicyclist Magazine Ad for New World War Model VW1M for War Work and War Transportation
Sept 2, 1942 - War Production Board Limitation L-52 Second Ammendment - Only Huffman and Columbia could build bikes (Page 6934 Fed Reg Sept 2 issue)
Sept 23, 1944 - Office of Price Administration ( OPA ) announced an industry wide restoration of bicycle production with some limitations. All bicycle manufacturers could, with some limitations, restart new bicycle production.
@cyclingday @Mark Mattei do you know when Schwinn sent out the information on the Defense Models? It would be nice to have that date here.