I have a saddle ring carbine in pretty good shape. It has a 20" bbl and I believe it to be one of the 1865 models that which had bbls shortened from 22" to 20" and converted to 50 cal, but I'm not sure and am basing this on a note I found in the Blue Book of Gun Values, 29th Edition. The bbl is marked PPM. Serial Number 1007 is on the frame but the bbl was marked 32966 with strikeouts over this number and 1007 added. Did this occur during the shortening of the bbl? Can anyone help me with the date of mfr and any other details? Many thanks, Hugh Brewer