The gun was made in 1966.
Could be inspector's mark.
Nobody knows this for sure.
No serial number = no way to answer.
Minor variations of the gun were issued with an A or B added to the end of the serial number. I don't think the exact differences are concretely documented, but the main thing is that the "B" was a particular revision of the overall design.
There was no B letter prefix assigned to the browning auto-5 shotgun serial number range.Please look again and list the complete serial number and any letters that appear before,during,and after the serial number.
If you mean a serial number on some product, it depends on what the product is. Each company can makes serial numbers mean anything they want it too.
That serial number requires a call to S&W
With the serial number that you have supplied,your Winchester model 52B was made in the year 1941.
With the serial number that you have provided,your Hi standard Model B was made by Hi Standard in the year 1936.
Generally, it means nothing.
Frame
It means that it is a duplicate serial number