Go to Browning's site, click on Support then date your firearm.
Your serial number indicates that you have a Browning light weight model auto-5 shotgun that was made in the year 1964.
If we are talking about a browning auto-5 shotgun,and the serial number is 1M not IM then your shotgun was a standard weight model auto-5 shotgun in 12 Gauge that was made by FN of belguim for browning in 1961.
Your Browning standard weight model auto-5 shotgun was made in the year 1954 with the serial number that you have provided.
The H prefix to your serial number indicates that your browning standard weight auto-5 shotgun was made by FN of belguim for browning in 1954.
The 4G prefix to your serial number indicates that your Browning auto-5 light weight shotgun was made in Belgium for Browning in the year 1964.
Your serial number indicates that you have a standard weight Browning auto-5 shotgun that was made in the year 1958.
Your belguim made browning auto-5 standard weight shotgun was made in 1962.
Your serial number indicates that your Browning light weight auto-5 shotgun was made in the year 1960.
With the serial number that you provided,you have a browning auto-5 standard weight shotgun that was made by FN of belguim for browning in 1955.
Your browning light weight 20ga.was produced in 1965.
47571.With the prefix of 1M to your serial number;this indicates that you have a Browning standard weight auto-5 shotgun which was made in the year 1961.
Your serial number indicates that you have a Browning light weight auto-5 shotgun that was made in Belgium by FN for Browning in the year 1963.