I finally managed to grab a picture of a local Triumph Stag. Unfortunately, it's at a mechanic shop on a busy road and my windshield was really dirty, but I was able to slow down enough to snap a pic:

IMG_7351a

It's a 73+ Mk2 for the starfish alloys, at first optional but standardised from Jan 76 along with brushed aluminium sill covers. But US Stags discontinued at end of 73/start 74 before the 74+ big bumper rules, and this sill looks painted - perhaps with anti-rust paint. So I'd guess a final-year-in-US example which has seen better days.