I don't know about rarest but I'll say the most common are. These three were very common. Stainless was an option from the start of M70 production in any caliber and nearly any configuration. Heck M54's had the option as well as far as that goes. It doesn't seem that many opted for the option. The three listed below were 220 Swift and 264 as mostly standard and the 300 H&H probably 40% or more, from my observation. I saw a 270 or two but honestly can't recall a 30-06! Probably folks held onto them??? But again, I have no idea of the rarity of Stainless in any particular caliber.
1. 220 Swift
2. 264 Win Mag
3. 300 H&H
