It is a "P" series M91. These used barrels that were re-lined. Finnsh P-series M91.
I bought 5 of them back around 1986. I sold 4 and still have one. I had sold the one I have but, the customer had issues with it so, I traded him another and simply kept the bad one. Mine will not open after you fire it unless you use a wood block to beat it open. I have tried every "sticky bolt" trick that anyone has suggested and nothing helps. If I remember they all looked like they had been re-furbed and then stored. Only handling wear.
Al