LGS had a "used". M9 contract gun of some sort on sale for less than $300  

On the right hand side of the frame says. U.S 9mm M9 Beretta USA
on the right side of the slide Assy 9346XXX-65490


Left side Frame M9-179XXX
Left side slide of the slide is a copy of the right side frame.  

not a Beretta guy at all. but for this amount and this nice of shape it was hard to pass up.   So I didn't and bought it.

Sounds like a mil-spec M9 so a 92FS would be the commercial equivalent but the M9 has several distinctive features that are different to the 92FS. We'd need a pic to be sure.

They made some commercial versions with M9 markings as a commemorative or replica. Came in a OD green cardboard box with M9 print.

Standard M9.  $300 is a great price.

The collector series that they used to sell had the PM marking on the slide, barrel, and assembly number on the hammer.  Regular ones don’t have those markings.

If you find one without the M9 prefix in the serial number as well as the PM marks and the hammer described above, it’s most likely a true military one and probably stolen government property.  

The only legit ones without the M9 prefix, are General Officer  purchased military ones that are legit and not stolen, but extremely hard to come by and go for big $.  

Edit to ad that some, but not all General Officer purchased M9’s, have a GO prefix in the serial number.

Excellent deal you got on the M9.

Nice score OP!!! Shoot that bad boy, there’s a bunch of reasonably priced mags in the EE right now!

Commercial M9s are a dime a dozen, but you paid a nickel!