You did not provide a serial number. You will have to call Browning.
Your Browning auto-5 shotgun with the prefix of 70s to the serial number identifies that your shotgun was made in Belgium for Browning in the year 1970.
By the serial number.
by the serial number on the bottom of the receiver
Serial number 1
It was made in 1949.
Your browning auto-5 shotgun was made by FN of belguim for browning in 1957.
Your sweet sixteen browning auto-5 shotgun was made by FN for browning in 1963.
Your belguim made browning auto-5 standard weight shotgun was made in 1962.
If it is an auto-5 shotgun than 1938.
This is a 12ga. made in 1937