The term "acier special" is found on many Auto-5 shotguns. It is French for "special steel". The stamp "acier special" found on barrels are for Fabrique Nationale guns, and NOT Browning Arms Co. guns. Fabrique Nationale (FN) was the manufacturer of all Belgian Browning guns. Browning was simply an importer and bought guns with their name on them to sell in the United States. FN was licensed to make and sell some of these models World Wide outside the US. If it says "acier" on the barrel then, you probably have an FN gun. It's possible to have one of these barrels fitted on a genuine Browning gun, but then the receiver would identify the mix & match. FN Auto 5's as a custom, used the term Browning patent on many of their guns along with acier special. These guns never were sold in the US, but somehow made it to the states from overseas. Many guns were brought by returning US servicemen from WWII and so on.
your browning auto-5 was made in 1923.
Your browning auto-5 shotgun was produced in 1931.
50-250 usd
Browning's web site has a sn search function.
$350-$850
1932
Basically impossible to value with no other information.
The 2S prefix to your serial number indicates that it was made in the year 1962.
50-500 usd
If your browning auto-5 was made in 12gauge then it was made in 1925,if your shotgun was made in 16gauge then it was made in 1929.
Acier special means Special steel, and barrels marked this way are only on FN sales guns, not Browning. FN produced the guns for sale outside the US and were not imported to be sold by the Browning Co. The FN version is mechanically the same as the Browning version, but markings and finish may be different.
With the serial number that you provided,your Browning 16 gauge shotgun was produced in the year 1949,by FN of Belguim for Browning.