I don't think worn coil stops would cause the problem you have.

usually the issue is the mechanism is gunked up. Can you easily pull in the coil plungers with your fingers and get a crisp increment of the numbers without feeling resistance besides the initial get-it-moving? if not, time to take the register apart, clean and use a modern thin lube to reassemble.

see http://bingo.cdyn.com/techno/overhaul/magic_ring/replayreg.html - tho that page probably needs some editing for clarity ("editing" = complete rewrite).

green book says part number is A-613-2A - "core plug assembly". It's not a typical coil stop as it acts a bit like a shock absorber and the part that goes into the coil is on the opposite side of the bracket from a standard coil stop.

'course, that part number is for the later 4 digit register. Don't remember if the dimensions are different.

if ya get stuck, I'm sure I can scrounge something off parts games next time I go to the pinball museum warehouse if the pieces on the yacht club register I have at home don't work.

o-ring...great idea!

afaik, the cover plate was that light green on all the games until Magic Ring in 1968. At that point, black and bare metal ones started showing up along with the green.

the green usually has chalked/faded a bit, so if you take yours to the store to match a spray paint can top, err on the side of darker green rather than lighter.