It was converted to .45 Colt, yes?
British, then Canadian
usage, I reckon.
If you can find any recent completed auction prices on the various gun selling sites it would be the best way to estimate current pricing on a national level.(I don't have an account on any, so can't access the old completed auctions.) My SWAG would be anywhere from US$450-700. I know that's a pretty wide range, but that's what I would expect insome of my favorite stores. Even in a fairly limited geographical area its not uncommon to see such variances. On particular occasions, that range may be even broader. (Being a regular customer also helps keep prices toward the low end!)