Beretta was tagging gauges cal in the 60's and 70's which is what I'd presume this gun's vintage to be.
Strange, none of my Berettas from the 60s has that and I didn't think they made the 6 series that far back but then again what do I know, I am just a fan and no expert!
I don't think that's a 6 series, more likely an S series, just guessing but I'd say an S57.
I have a Beretta 409 which is the early Silver Hawk SXS made in 1960 which is stamped 16 CAL
This is a 68- series gun made for the British or european market, not terribly uncommon in Canada but never imported into the USA. The previous S 5- series guns had the cocking lever exposed in the bottom of the receiver.



























