As other have said, this is a MX-6707/VRC matching unit.
Ref:
http://www.public.asu.edu/~nate123/C...io%20Setup.htm
http://www.armyradio.com/arsc/custom...&cat=82&page=1
Antenna - Used with vehicle installations which have the radio sets AN/VRC-12 series, AN/VRC-53, AN/VRC-64, AN/GRC-125 or AN/GRC-160. The matching unit MX-6707/VRC tunes the antenna elements automatically or by manual selection via a selector knob on the base.
The whips are most likely still good. DO NOT use the MX-6707/VRC ATU. It is cracked, and if you have the whips on it and drive, it will crack again, and the entire top of the ATU and whips will fall off your vehicle and end up on the road, or in the windshield of the vehicle behind you. Don't ask me how I know........... There are lots of the MX-6707/VRC around, no need to install a defective unit.
Cheers!
Stuart