L.Brown, I do not have handy the book by Crudgington re the 12/20, but I am pretty sure you will find reference to the 12/20 there.
Although I own one of Birmingham's "best" my favorite is not among English guns at all. So believe me, there was no intention to favor one English city over another. However, knowing how the trade functioned, it is likely that no London gun was 100 per cent London made. The same is I believe true today. As far as I know case hardening, barrel blacking, and some other jobs are still handled by outside shops, mostly not in London.It is possible that with current environmental regulations such jobs are by necessity carried on outside city limits.
The definition of "best" that includes manufacture in London reminded me of Gough Thomas' comments re Burrard's London bias. Understandably so since Thomas lived near the New Forest and Burrard in West London.
