The 72S suffix to your serial number indicates that your Browning superposed shotgun was manufactured in the year 1972,by FN of Belguim for Browning.
Superposed
Your Browning lightning superposed shotgun was made in the year 1968 with the serial number that you have provided.
The lightening model is essentially the same as the regular superposed, with several weight saving modifications. These include slimmer forearm, lighter barrels, and small internal changes to the receiver. All in all, the weight savings are about a 1/2 pound. -jimmy
With the serial number that you provided,your Browning superposed shotgun was made in Belguim for Browning in the year 1955.
Browning Superposed Shotgun
It is the model name of the first Over/under shotgun that Browning made. "Superposed" in the dictionary means "one on top or over another".
John Moses Browning. The Browning Superposed was the first practicle over, under shotgun
If it is a Superposed model 1951.
Does not exist. However, there is a famous over/under shotgun made by Browning call the Superposed.
The name is Superposed. Find this book - Browning Superposed: John M. Browning's Last Legacy by Ned Schwing
1935