I was holding out on posting this one but after flipping TH44 a bit of s**t about not posting his Gibbs, I feel obligated...
I don't know the actual history of this rifle but here is what I "think" is the deal.
The rifle was originally built as a best quality back position match rifle, APUN 350. The section in the top of the heel of the stock where the rear sight was has been filled in with a piece of horn or black plastic.
The gun was rebarreled by Gibbs(39 Corn St. address near the breech)with a 29" ovoid barrel in 303 British. I am not sure if it was rebarreled for sporter use or as a smallbore match rifle at this time. The reason I am unclear on this is that there are two dovetails in the barrel rib - maybe it could have been done as a scoped 303 target rifle (?). The dovetails are filled in with blanks and the current scope bases are dovetailed into these blanks. The bases are "Vienna" style quick release type. Nice that there were not more cuts made in the rib...
There is a Gibbs pattern sporter forend on it now - not sure of its vintage but looks to be fairly old, maybe as old as the barrel job...