Value is too difficult to be accurate without seeing the gun. Condition which includes the amount of original finish and original configuration will determine value. Auto 5's with poly-chokes, compensators and recoil pads (other than Mag 12's) will reduce value. Near mint guns and original box will command an extra premium. Recommend taking it to a gun shop for appraisal.
Your browning sixteen gauge shotgun was made by FN for browning in 1949.
Your browning sweet sixteen shotgun with a 5s prefix dates your shotgun to the year 1965.
Your browning sweet sixteen shotgun was made by FN for browning in 1928.
The serial number prefix 1S was assigned to the browning sweet sixteen model of the auto-5 shotgun in the year 1961,So yes you have a Browning sweet sixteen shotgun.
That is not a Sweet Sixteen serial number.
The Sweet sixteen name is the model of your Browning auto-5 shotgun!Is the number 51666 the serial number of your shotgun?Please re-post your question so that a answer can be provided.
With the serial number that you provided,your browning sweet sixteen shotgun was made by FN of belguim for browning in 1928.
With the serial number that you have provided,your Browning Sweet Sixteen auto-5 shotgun was made in Belgium for Browning in the year 1957.
Your browning sweet sixteen shotgun was made by FN in belguim for browning in 1960.
your browning model auto-5 shotgun sweet sixteen was made by FN of belguim for browning in 1967.
With the serial number that you have provided,your Browning sweet-sixteen auto-5 shotgun was made in the year 1952.
Your serial number indicates that your Browning Sweet sixteen auto-5 shotgun was made in the year 1961.