First, Welcome to the Forum.

Selmer Paris is totally different from Selmer USA.

If you are looking at vintage pro line horns and even pro line horns made by Selmer Paris today, they simply go numerically higher as the years advance. The serial numbers do not differentiate from alto tenor Bariton Sopranino whatsoever. It simply depends on which horn was manufactured next, depending on their orders to produce them. So you can have a tenor 116748 and the next horn an alto at 116749, Circa 1964 on the serial number chart. In other words there are no horns with the same serial number, one alto and one tenor.

Selmer USA simply is a stencil of a taiwan producer today. No horns are made in the USA anymore. You can even get your own stencil from a Taiwan producer today. I believe Tenor Madness has a stencil from a German or Belgium producer and Saxquest has one from Taiwan.

I hope this helps. I am not familiar with the serial number lists of todays horns. I deal mostly in vintage American horns, and vintage European pro line horns. But you can contanct Selmer/Conn and they can probably help you by a phone call if nobody steps forward and directs you here.

Good Luck

I have been working with two Vintage Selmers (Paris only) in the past month, asking myself this exact questions.  From my research, the best I can figure is the following.

1). The serial numbers  are going to help you identify the year of production pretty reliably.
2). The year of production is a pretty good indicator (but not perfect) of the horn you have.  

Most people do not believe it is the case that  in 1953 Selmer stopped making the SBA (official Super Action) and in 1954 they started making the Mark VI.  (As the Selmer Paris serial number chart would lead you to believe).

Professionals seem to indicate that for a few years before and after the 'changeover' indicated on websites, horns of multiple versions were made and some were hybrid (partially configured for a SBA and partially configured for a Mark VI, for example).  This could have been done for consumer testing or experimental reasons......or it could simply be that repair shops could take parts (they had in inventory) from one of the horns and use them for repairs on the other model.  Repair shops could be the source of the 'hybrids.'

If you have a 1958 Selmer Paris Sax - that is about 4 years into the Mark VI production - so it is most likely a Mark VI.  If you had a '53 or a '54 model, you would would probably need to do additional research to determine the identifying characteristics of the specific sax you had in hand.  

1946 - 1950 would be another window where you'd have a larger question as to whether you have a Balance Action or a Super Action.  1972 - 1976 would be a window where you would question whether you had a Mark VI or VII.......etc.   There are bunch of changeover years.

Good luck