Frank Iannamico asked me to post this as a pinned post here in the M3 forum. This is a revision to his book on the M3 Greasegun.
M3 Book Addendum
During subsequent research the author of this book discovered that the reported 15,469 M3A1 production figure was actually a typographical error in the Ordnance Department’s Log of Significant Purchases. The actual Guide Lamp M3A1 production figures are listed below. These corrected figures were obtained by the author from the Cincinnati Ordnance District records that the Guide Lamp plant reported to during World War II.
Guide Lamp M3A1 PRODUCTION (1945 only)
August: production canceled.
Total submachine guns manufactured from 1943 to 1945 by Guide Lamp: 606,694 M3, and 82,281 M3A1 models, for a total of 688,975 weapons.