1) I didn't see any stamped dates/codes on my gauges...
2) My car (which the gauges came from) is a Sept '69 (09C) production date (late, which might explain the 'smoooth' finish, vs the 'brushed' finish question you asked?)
3) The difference between production parts and service parts (re the 'crinkley corner bends') could be a change in Al alloy, in addition to a change in supplier?
4) I'm confident you noted the similarity between the bright orange fluorescent and 'hugger' orange?
The names may change, but it's still 'hugger' .. just with a fluorescent glow..
Changing of material is probably true.
As for the color... Whatever helps you sleep at night..
I think Im gonna substitute Hugger Orange with Carousel Red when Im talking to you from now on out.