Setting price on cav 51

[firemun]

I have a couple of cav 51s. Both are set up on free play. How and where do I make the change so that they are coin operated. I can't keep the neighborhood kids out of my garage. I don't care if I can only set it to need dimes or nickels. It is a National brand on both. Any ideas.
Thanks

[johnieG]

Can you show me a shot of the coin mech? and is you machine
originally a 10 cent vendor? hope I can help.