Mines a 1993 era gun with a BPZ serial prefix. It came with the aux .22 LR cylinder, wrapped in plastic in the factory box. Instruction to change out the cylinder is a small sheet that was taped to the inside, top of the box.
I believe it came with rubber grips, I replaced them with the wood grips shown.
M-39, I really like your pair of 651's , especially the two incher.
FN in MT