Just in case you haven't found out yet....
The marker buttons (with the 5 numbers on) are used for placing neighbours bets.
They are usually placed on the wheel with the denomination underneath (usually £5 minimum for each number making it a £25 bet).
Most of the layouts have the wheel with the 3 sections marked on them now instead but the markers were in use during the 80s and 90s and probably before too. They were kept in layout order in an unusual "rack". I have a few from Crockfords when they upgraded to the cloths with the wheel type. Red and black (with the green for 0 too) helped make it a little quicker for the dealer to find the right one and was one of the many gripes a dealer would moan about if left in the wrong order. Obviously it is for the UK style wheel with a single 0.
I hope this has been of some use.