There are a number of armored car services listed in the Chicago area Yellow Pages. Of course, probably not all of them handle ATM servicing. It might be effective to contact some banks in the area with offsite ATMs (you're certainly not the first bank to do it) and ask to speak to their ATM department heads. Then see if you can get some names. You'll have to carefully identify yourself and your purpose in calling, or you'll get their security radar going and you won't get far with them.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8