Here is where one has to do a bit of research and then take a leap of faith. Browning never imported any Auto5s into the US with a Poly Choke but that being said, they did import a handful into Montreal with factory installed Poly Chokes but those are pretty difficult to come by. All have ribs fitted to the barrel and Poly Choke. When compared next to an Auto5 with one put on by a gunsmith, you could pretty much tell which one is the factory.
It must have been a trend because companies such as Mossberg in the 1960s and less so up to the 1980s put a lot of 'Select' or 'C'lect' or 'Select-a' etc, factory chokes on their shotguns. It was never Brownings thing so they jumped off the bandwagon pretty fast. Even if you know these things exists out there, be careful that it is not one that was added on after. A lot of Americans added these adjustable chokes on because they where readily available in the US. As far as I know, Browning only had a very short contract with the 'Poly Choke' company. Poly Choke still exists today and if you call them, they will confirm that they sold X amount of adjustable Chokes to Browning and shipped to Belgium but aside from that, they do not know which guns they were put on or for that matter, if they were even used. Unfortunatly FN Browning only kept very general records and do not have any details as to which Auto5 got what either. A Poly Choke does make the gun more usable and are rated for steel shot even though Browning 'special steel' (which is harder than regular steel) is not.
