Doug, you are correct on all counts. I noticed the horn triggerguard right away as I have run into this material on other guns I own.
Some things I didn't mention in my first post: a) the gun has a set trigger for the rifle barrel which is available when the top selector is in the proper position; b) the barrel length is 23 5/8 inches;and c) the chokes are, as best as I can measure at the moment, a very tight (European-ish) Mod and Full combo. Or maybe I should say almost Full and XFull?
Do you have the scope?
Unfortunately not. [Sigh.....]
The original owner discarded the scope and claw mounts apparently due to recent flood damage/rust before he passed it along to my father. I am looking to have this omission remedied in the near future. I was looking to check with Joseph LeBas at LeArmes, but I just saw that he retired not too long ago. I will probably call the folks at NECG and see what their thoughts are on the project. I have worked with them before, and have had good results. I may also check with Doug Turnbull as he is only an hour away, and has also done exceptional work for me in the past. Additional suggestions are welcome.
Finally, I am still guessing at the reason for the '75' proof mark. If this gun was re-proofed in 2/74, as it appears, could it really have been proofed for a 3" shotshell. I've never seen one
commercially, but I suppose it could have been proofed at a corresponding 'pressure', or for 2.75 inch shells at USA type SAAMI specs and that is how they marked it on acceptance. Who knows the specifics... but I would sure like to find out the answer!