Hi all, I'm looking at a standard 63/66 Springfield conversion. Lockplate dated 1864, remains of an 1865 on the barrel, 1866 with eagle on the front of the receiver - all normal. My question is about the breechblock. I didn't think Springfield started scalloping/cutting out the lightening cut on the underside of the breechblock until a later model - model 1868 I believe? And of those I always thought it was the regular 'scooped' cut out. This one has two cuts scooped out of the block (leaving a central 'spine' down the middle). The 1868 has the full cut, the 1865 has no cut I believe. Might this be a 'transition' cut for lack of a better word? I thought normal model 1866 breechblocks had no cut out like the 1865.