Interesting /3

Went to the Show of Shows this past week, and found a very nice, unissued No 4 mk 1/3.
It reads FTR. 54, in electro pencil, with new serial number.
What is interesting is that it looks to be a scrubbed Long Branch. The receiver side wall and heel have been scrubbed and buffed. However, there is a remnant of the "L" on the heel, where the Long Branch serial number would be.
There was a /2 there that looked the same, same markings, was scrubbed, but had traces of the heavy broad arrow on the left heel. It was grossly overpriced, IMHO, so it is still there.
Is this that commercial BSA /2. /3. that I've read about?
I will try to post pictures soon.