In the last year I have seen half a dozen Westley Richards conversions to center fire. All are decently done, but some are real works of art. Amoskeag Auction had one around the first of the year that was a conversion from a muzzle loading percussion, to a pinfire, to a centerfire. I was outbid by a well known dealer for the gun and he handles thousands of guns a year. But, he said this gun would go into his collection. The workmanship and condition of the gun was just the very best.
I think the one pictured is on the lower end of the conversion styles, as the pinfire hammers look to be ground off at the nose.
I do shoot those old conversions if barrels measure out ok. Lots of fun, now that I don't have to get limits every day in the field.
Here's the catalog description of the conversion Westley Richards I was referring to.
http://www.amoskeagauction.com/112/371.php