The Pre-64 model 70's all used the same overall length receiver. The bolts for the long and H&H length cartridges didn't have a piece like that, but the bolts used for the short cartridges; .243, .308, .358, etc. did have a piece similar to that. It was brazed onto the extractor retaining band and acted as a stop so that you didn't have to retract the bolt all the way back when cycling the action. The photo shows a .300 H&H, .270 Win and .308 bolts.