It is my understanding that the '0' series guns were all made by Beesley using his patents including his interceptor sear, 'self opening' action (often known at the 'wrist breaker') etc and can be found in both boxlock (see Joe's post above) and backaction sidelock forms. David Baker mentions this and says that he assumes that 'a deal was struck between HAA Thorn ('Charles Lancaster') and Beesley'. I had this information from a couple of other sources but am damned if I can remember where! Nigel Brown mentions the '0' prefix but does not comment on its significance other than that the guns were outsourced.