Having gone away and looked at the shutter on my Speed Graphic I have discovered it is a SUPERMATIC X shutter - ie strobes only yet it has the same style of flash contacts. According to the CAMEROSITY (1,2,3,4,5,6,7,8,9,0) system the lens on my camera has the letters ES on it - meaning the lens was made in 1947 - if it is the original lens on my camera then it dates it to the first year of Pacemaker Speed Graphic production! Using the CAMEROSITY system it should be possible to find out the age of the lens as well as finding out approximately when the Supermatics changed from F or M sync to X sync.
Hope this helps,
Lachlan