Afraid not. Brass is repro but BM is ‘possibly’ TA. Unless it has provenance it’s infinitely more likely to be repro than a badge worn on No. 1 dress as Alan mentions. There have been BM ones sold on websites as genuine, including regimentalbadges.com, sporting the large font post 1950s J.R.Gaunt London mark. My personal opinion is you do see repros with large letter Gaunt London mark (e.g.
https://www.britishbadgeforum.com/fo...5&postcount=33 and
https://www.britishbadgeforum.com/fo...36&postcount=1) so I do not buy that this mark gives any credence whatsoever. Again like so often with SF items, for me it comes down to provenance. There is also a thread claiming these Gaunt London marked BM badges were for wear at the coronation, again I find this fanciful.