Model BB vin number

[Marshalfire]

So, I have a frame with a vin number BB 3 5072995Y!

What is the 3 indicate, and what is the Y at the end mean?

What I have found by the 5072995 that it was produced sometime between 1932 and 1934.

Nothing on the 3 or the Y though!

The frame is bent but would like to know the facts about it even though I do not plan on using it!

Any help would be appreciated!

Thanks!