I have a question. Where are you finding information on “X” stamped helmets? I just acquired one with an X stamp and I am looking for information on this helmet. Thanks
A good place to post questions on US military equipment is the US Miliataria Forum.
U.S. Militaria Forum
They have a section just for WWI era equipment.
WWI US MILITARIA - U.S. Militaria Forum
Sorry couldn't give you a better answer. Most of my research notes are packed away, plus I can't recall off the top of my head any sites with the X helmet code information. Give me a day or two to see what I can find. The information below is what I can confirm with the research I've done, the list is not a definitive list, just what I have actually seen. So if you have a X marked helmet I would love to see pictures of it and the markings.
Known Helmet Manufacturers of WWI American M1917 helmets:
Edward G. Budd Manufacturing Co. 1,150,775 made
Sparks, Withington Co. 473,469 made
Crosby Co. 469,968 made
Bossett Corporation 116,735 made
Columbian Enameling & Stamping Co. 268,850 made
Worchester Pressed Steel Co 193,840 made
Benjamin Electric Co. 33,600 made
Known Heat-Stamp Markings of WWI American M1917 Helmets:
(This list is based on what I have actually seen, more heat stamps might be out there)
UC
XH
YJ
ZA
ZB
ZC
ZD
ZE
ZF
ZG
ZH
ZJ
Known Liner Manufacturers of WWI American M1917 Helmets:
Leatherwear Co of America - Brooklyn - New York.
A.J.Bates - Webster - Massachusetts.
L.C.C.&.Co - 1917.
R.H.Long.&.Co - 1917.
A.E.Little Co - Boston.
F.M.H.S. Co.