The su85m was the chassis of the su100 with the 85m gun.The 100m wasn't ready for production when the su85 production was cancelled.Thus this is the stop gap measure of which you speak.Once the bigger gun was ready to go su100's went into production.I remember PB.Was the game for tactical nuts in the day.I recall after ASL came out PB,PL and AIW just gathered dust on the shelf.(Well at my house anyway )