The new photo shows what I believe to be the only version of the SA extractor plate design. As I understand it, the Pope design has the bore offset high and the extractor was not substantially (though claw may have required a bit of reshaping?) altered.

The plate design (what a Rube Goldberg nightmare!) has the bore offset low, with spring-plate pulled out by normal extractor. Interesting about the trip. The first picture shows a white spot, which I took to be an empty hole - guess it wasn't. Barrel is also interesting - having seen the interior shot, I'd have to guess that it was re-profiled as well as shortened - doubt very much that anyone would go the trouble of replicating the plate, etc. Was going to say that it could be restored - now, that's impossible.

Cannot tell if that is the special CCV cartouche. If it is, and if it were mine, I might consider offering the stock to a collector to be stretched, and then putting a nice classic sporter stock on the shortened .22, which is beyond saving so far as originality is concerned, but could be a knockout plinker.