Claude - My opinion is that what you have is a authentic BM59 put together by Reese. When Bob Reese brought the BM59 inventory back to the USA, there were receivers that weren't maked 'Beretta', they were blanks, but finished. I got in 2 Nigerian rifles back in the early 80's (I'm a dealer) and they were marked Springfield Armory, customer questioned me and I contacted Reese. I received a letter stating that they were original unmarked receivers that Reese marked with their name. The serial number seems about right. As far as the sight adjustment marked left, a lot of parts from the US were sent to Beretta, real good possibility that they came back. I took off my rear sight on my BM62, and the cover was marked H&R (Harrington & Richardson), I don't think anyone really knows since a mix of parts were used in the construction of the Reese rifles. My BM62 has a 'K' prefix for the serial number - I called them on this and was told that Bob Reese thought that there were duplicate serial numbers, so he prefixed some of what he had with a 'K' - HTH