This is on a stock buckle with a London Lion Passant of the 1740 —1756 period. One mark on the chape, one on the frame and both incomplete !
Ex Martin Gubbins collection, whose notes indicate that he and W. Wilkinson concured that the makers mark (in very Gothic script ) was L T. Assuming we all agree which way up it is ! Certainly the London date letters for 1846 and 1854 (L and T) appear to be the same as these letters.
The decollated edge is very distinctive.
No clues as to whose mark it is — almost undoubtedly in the lost smallworkers ledger. This is the only example of the mark I’ve seen, so the silversmith may well have been a general smallworker, not a buckle specialist