Hmm, need to check my part kit L1A1’s John, as one of them has a SP TMH but am sure retains original serial number.
Must admit I can’t see any evidence on the upper of original designation being linished…….but out of curiosity I blew the dust off my conversion kit box, as Peter states:
Conversion kit 7.62mm millimetre rifle .22 inch calibre L12A1
Is on the inside label..