Yeah either a frequency counter or a scanner with signalstalker (rs name) or closecall (uniden name) built in. Since you don't have any scanners like that at work, are you allowed to take the radio with you?
If so go to a radio shack and ask to look at say a PRO-97 and have them demonstrate the signal-stalker feature, then simply key up your motorola and it will display the transmit frequency. Another thing you can do if you want is to remove the battery from the radio and post the entire serial number of that radio on here.
Someone will be able to tell you at least what band it is on. Could be VHF, UHF, 700mhz, 800mhz or 900mhz. Just curious, what or who do you work for that uses those?