I have never seen or heard of one.....but .logically ,it is the first of the "new" series Burmans from 1930 onwards,the missing "A" from the B,and C lineup......incidentally the P means pivoted mount ,a patent of Walter Moore,while he was at Norton......BSA first infringed the patent,deeming it "fraudulent",then losing that argument,worked around it ,the first BSA having a Moore pivot was the SA A7/10 of 1954,long after the patent expired.