Lee Buncher kindly send me photos of his gas detection brassard that has a marking that wasn’t in my list yet, although it’s similar to the others.
You can see the list of markings here.

I still haven’t found out more about the meaning of these markings. I’m guessing JL&S was an abbreviation of the manufacturer and the other numbers dates and batch numbers. If anyone knows more about this, please let me know.

And if you have a gas brassard with a marking that’s not on the list yet, please share a picture of it, and I will add it to the list.