Hello, I could use some help interpreting the proof marks and general date range of manufacture on this Fred K Williams 12 gauge. It's my understanding that Fred Williams stopped producing guns in 1950, not sure where the 120025 serial puts this one. It looks like it was sleeved in the 80s as well. Top engraving is the "Fred K Williams London Birmingham" mark. Appreciate any help with identification.

[Linked Image from i.ibb.co]
[Linked Image from i.ibb.co]
[Linked Image from i.ibb.co]