Have owned several and rebuilt both varieties. Seems the "BP" model commands the most attention as it has the "Boost port" cylinder. Bottom line, put a sharp chain on both and telling the difference between the 2 running stock is splitting hairs. But for most collectors, the rarest one always command s the most. So I broke down one of each to help ID either one the best I could with the cylinder on and with the cylinder off.

Use this info as a guide but not as a definate/final verdict! The Pioneer Pseries saws (P-61,P-65, ect.) that were still being used by owners in need of a top end were being rebuilt with the up dated BP "boost port" cylinders around 1998.