Value and Information on a WHT Shotgun

Hi,
I am hoping for some help on a shotgun I have which is a side by side double barrel with external hammers. It has WHT stamped on some parts and in the centre of the barrels on the top it has what looks like WH Tisdall Bermingham or something with similar spelling. The S/No I think is 12434 and the barrel has 'not for ball' also stamped on it and there are some other numbers as well. Someone told me it was a William Henry Tisdall shotgun from Birmingham England, not sure though. If anyone can tell me any information about it or a site that may have some information about it it would be appreciated. It's not in restored condition an the stock is fairly bad but the rest may be good for spares. Not sure what it's worth or what to do with it.