A few years ago, I bought an all-matching 1950 SKS (I think Tula, but my bad leg and a flight of stairs are between me and the rifle) with a spring loaded firing pin. Got it for a very low price because the firing pin was either broken or missing. Was able to get correct parts and reassembled.
From time to time, I've wondered about how uncommon this configuration is. Would appreciate any comments or insight.