When I first started doing the letters I noticed that Parker used the word "Prim" or "Prem" or "Prm" pad when describing the recoil pad used on a SBT. Interestingly enough, I've never seen the word on a Parker SxS in the order books. I posted a picture of the word on the forum but nobody knew what it meant. I searched the internet thinking possibly it was the name of a manufacturers pad but came up empty. I figured it was just an abbreviation of the word Premium but that's just a guess.
Here are 3 pictures of the order book entries. The first 2 are from early 1917 when the SBT was introduced. The 2nd picture shows Prem crossed out and a Jostam pad substituted. The last is late 1919 (A-1 Special). Our order books ended Dec 1919. The stock books never mentioned recoil pads actually used on the guns. I've seen more Jostam pads and even a 3 ply sponge rubber pad asked for in the later 1919's. I think I'll call the factory and ask them what the word is