Non-availability of many Long Branch records was a cause for concern in my studies on North American production. In contrast, we have a good array of Britishicon and Australianicon factory records. Digital photography and computer programs make almost anything possible today, so a photograph is no longer sufficient proof. Agreeing with Peter, one needs to examine the item hands on before venturing an opinion. Such markings used a roll die and such a die would hardly be made up unless there was a reasonable production run. It is odd that we've never seen a Long Branch No.5 rifle, there is none in any official collection that I know of, nor have we seen any report on same. I would need to see the rifle/action body and consider it along with the other component parts.
Life would be dull if one knew everything, that is for sure.
Cheers, Ian