BSA Commercial No1 Mk3.

[Bindi2]

BSA built no1 Mk3 and Mk3* rifles to military specs without the crown stamp. To shoot at Bisley you needed a rifle of military spec to compete. The only way to do this was by buying a BSA get it passed and stamped so you could compete.
BSA also supplied other countries these rifles as well. who applied their own stamps.. This has created a huge area for collectors.