The gun is basically a 28 bore Webley 700.

The 700 was Webley's biggest selling model and it is a decent, nice-handling gun, though I have to say i am not usually impressed by the examples they were making towards the end of their existence.

I have a 700 i 12-bore and it is anice gun to use and not overly expensive - certainly not a 'best' gun but a god one for everyday use.