You will have to call Browning with the serial number.
Your serial number indicates that your Browning light twelve was made in the year 1955.
If it is marked Light 12, that is an incomplete serial number.
1958
1979
This gun was made in 1953
This gun was made in 1955
1973
50-500 USD. Browning will have to tell you the age.
Your browning light twelve was made in 1972 as the number prefix suggests.
your browning auto-5 light twelve gauge was made in 1960.
the 9Z prefix dates your browning to 1959.