Look for? Refinish! Even if it is a refinish, as long as it was decently done (Watch for a bad polishing job) it still should be in the $600+ range.
If it is one of the Brit contract guns, is it still in the original.
.455 or has it been converted. If so, to what and how.
(Still should be in the $600+ range)
Now if it's a converted Brit that has been badly buffed and reblued, you might be getting in a little deep, and it would depend on how bad you want a TL.
Overall visual and mechanical presentation should be a big factor.