I finally got the photos from the owner. Files were small, and the pics are not too sharp, but I guess they should help in any case.


As I may have said, I'm not familiar with Greener models. I googled images of various models, and this seems to be an F model. I found a photo of
F16 (?), which had similar thin action swells as this one. That F16 was the closest that I could find.
Models like F20 or FH35 were otherwise fairly similar at first glance, but at least the swells seemed to be bolder.
Photo on proof marks is poor also, but can any of you, who have seen a lot of these, figure out the marks?
I phoned the owner the other day, and he said that the chamber throats look different than in an average 12ga shotgun, so this might well be for brass cases, as was suggested above.
Regards,
Saku