What I meant was, was the Bofors known as 40mm L/60 before the L/70 entered service, I'm not sure it was. Hence being marked L/60 indicates it was to differentiate between it and the longer L/70 barrel.
Having just checked all my manuals which date from 1941 to 1947, it is only listed as Ordnance, Q.F. 40mm. I suspect it only became known as L/60 in British service when L/70 came in during 1953.