"London" Headstamps

The following are “London” headstamps on .450 Short Revolver rounds.

Number 1: From the style and construction this looks like Sellier & Bellot production (S&B had a London address from 1891-1893 which might explain this).
Number 2: Don’t know!
Number 3 and 4 - are from the same [unknown to me] manufacturer and are identical in case, primer, bullet and crimps. The only difference is that the headstamp caliber has been removed. Since it is on a 450 it could mean that a bunter from another caliber was adapted by grinding off the caliber.

1). Has anyone seen this headstamp on other calibers?
2). Has anyone seen a box containing rounds with the “London” headstamp, regardless of caliber, that might indicate the manufacturer.