FM BUILDERS PLATES

I have always woundered where the FM Brass Builders plates ended and the stainless Steel plates began. I had to good fortune to look at a collection this past weekend. In the collect was AC&Y FM plate number16L831. It was brass, I own SP 12L834 which is Stainless steel. Since AC&Y owned 21L832 and SP switcher order began with 12L833, I would think that the Last brass plate was 21L832 and the first Stainless steel plate was 12L833. However , if FM used delivery date as the dividing point you might have a mixing of numbers between brass and stainless steel.

I would assume that FM went from Brass to Steel after WWII? As Steel was in much higher demand than Brass at that time. Thats just my guess thow.

The change from brass to steel was sometime after 12/1955. FM stayed with brass plates longer all other major builders