Well, that's a pretty high level seminar on shotgun construction for sure.
Thanks for the valuation Rocketman. Have your spreadsheets but didn't think about using them yet. Only modification to the info I've provided is that the triggers seems to have original case hardening clearly visible on them which makes this more of a safe queen than I thought, perhaps.
And definitely two screws on the bottom of the action as this quick photo shows.

Certainly learned more about this gun and boxlocks than expected! Thanks to all for the contributions. Now, if it shoots well with my 2 1/2 inch loads and I get that sling swivel fixed, it will be lots of fun.