there was definitely some sort of code:
🔗Wheal-Jane-Tin-Mine-Archive-Album-Image-32811[linkphoto]Wheal-Jane-Tin-Mine-Archive-Album-Image-32811[/linkphoto][/link]
there may be a better example on here somewhere, colours are pretty hard to discern in the photo, also doesnt mention fitters (unless its above the others) the yellow bezels at Jane were evidently production miners. I guess it was like a lot of things in mining that were supposedly standardised, the standards were there but still each mine could have been different!
Im aware that Oldham offered bezels in: black, white, yellow, green, red, blue.