“Priced to sell” - if they sold it at Holts they would need to get a hammer price of at least £3,600 to end up with £2,700 in about 4 months time.
If it had 2 3/4” chambers (like my £43 Tobin !) they would no doubt be seeking a bit more. Standard steel in 2 1/2” is regarded as being a bit short ranged, 2 3/4” somewhat less so.
If that gun was here in the states, some dealer would have it priced at $19999.99, and it would sit for a minimum of a decade. The single trigger would be seen as a huge plus, and several morons would be looking for somebody to put a beavertail forearm on it. About 1 out a 100 or so would have any grasp at all about what the proof marks represent, and 1 out of 500 might know what a 2 1/2” chamber is.
All that said, let’s see some more photos of your Tobin. We don’t see those every day, or, an Englishman who owns one.
Best,
Ted