This one is a bit curious to me. I've long collected portrait miniatures, and while I love this image, it feels to me as if it's one taken from what more likely would have been a shagreen or leather etui, and mounted into a 1800s Victorian era brooch mount. The old cased images' cases haven't all survived well, and it would make some sense to want to keep an important family portrait. I could be wrong, but part of my impression of this one is that it's small for the mount, but not in the typical way, which would shrink it slightly and allow border inside to show. This one either needs to be adjusted in its brooch, or it's been slightly cut for the brooch mount (see images to understand). The gentleman is Georgian, but I think the mount is perhaps early to mid-Victorian (c.1840-50). I could be wrong. The convex polished cover glass is also consistent, as is the long pin back and c-clamp. It does test as 14k gold, which might be 15k if English. I bought this from a French collection some years back. I'll pass him along at cost for the inconsistency which has always bothered me a bit.
All of that said, it is in very good to excellent condition. The backing is not karat gold. The pin tested 12k. Beautiful, elegantly dressed man c.1850-80. Convex cover glass is also excellent.