After a bit of reading in Gabriel's book on 410s, I think it's possibly a Northwood model H&H. If so, it was one of possibly only four produced. S/N' 37140, 37141, 37443, and 37021.
I think I see that your gun is 37021 from all the pix. Gabriel says: "... A fourth 410, SN 37021, sold in May 1961. It has double triggers, ejectors, and 27-inch barrels. ..."
In a previous paragraph, Gabriel states: "This Northwood gun was made 'to Holland & Holland specifications" off premises but 'shot and regulated' by Holland & Holland to a very high level of workmanship. A Birmingham consortium led by Vic Simmons built these guns. ..."
If your gun is indeed 37021 as I think I can make out in the pix, I'd recommend you buy Ronald S. Gabriel's book; American & British 410 Shotguns, if you don't already have a copy.
regards
Chuck