vending machines with individual buttons for each item: braille indicates what's inside
vending machines with codes: braille indicates what number/letter corresponds with the button....
on their first try a blind person will need to ask for the number, but once they know their cheetos are under C-11 (as mentioned) they can select it on their own...
now most blind people will remember the position of the buttons without any problem, but if you have to select out of 30+characters, it's always easy if the corresponding character is written on the button in braille....
so it's just to facilitate them while pushing in their code so they don't accidentally push D-11 instead of C-11 and get some skittles instead of cheetos ...
that's just my 2cents....
and FYI they identify coins/notes by size/form
i'm not blind but i can recognize all euro coins just by feeling them, also the euro notes go from low value=small note to big value=bigger note so they can also be recognized by touch.....
hope that helped :)