Thanks, love those pix, not so much because I love the piece, which I don't, but all the stuff to critique on it!
I've never seen that version of Strong 8 GA. tube before, with the swinging hammer. I've seen smaller bores with that feature, however. Notice how the trunnions had to have large bushings installed after-market to adapt it to that apparently home-made carriage. I've never seen any version of a Strong 8-GA., even completely original in mint condition, sell for anything like $25K. I've seen some of the very largest Strongs sell for that kind of money, such as a Strong 1-gauge on original field carriage with original limber, in mint condition, yes. The thing pictured here, no. So it will sit there a while. If I were looking to buy a Strong, I'd keep looking until I got one that was all, or mostly all original.
Can anyone read what's stamped on the muzzle? That also looks like an after-market mod by some owner, since I've never seen a Strong with any muzzle marks.