In my long-running quest to get the right tang sight on my rifle, I recently got hold of the above sight to try as a stop-gap measure.
Just wanted to say that even though it took a fair bit of fitting, once installed it's proven to be a really excellent barrel sight, giving a fantastic sight picture without obscuring the target like most rear sights do. It also seems to be as nearly accurate as a hunting tang sight except for the lesser sight radius. Sight acquisition of also nearly instantaneous. But of course you're not getting the windage and elevation adjustment of a Vernier or whatever.
Anybody who isn't too bothered by the fact that it is not strictly authentic and wants what is probably the most accurate of any barrel mounted sight with its attendant durability might want to have a look at one. For a hunting sight I don't see how you could do better.