As you have found out this is an RCA 700 Series Repeater they made these circa 1970. It is presently been modified as a HF cross band repeater. 14.266mhz is a general use frequency in the 20 meter hambands. 18.277mHz is an odd one the only reference I can find is the frequency was assigned to Friday Harbor, city of Anacortes, Washington State. station WHV382, and is used by Sailmail ( http://www.sailmail.com/) which is a email service for Yachtsmen. For what it is worth here are the manuals http://www.repeater-builder.com/rca/rca-index.html
As for a getting it up and running, don't even bother the modifications are undocumented. I don't understand how the got a repeater that is designed to operate 6 meters, VHF, and UHF to work on HF; is this the reason why it was in that landfill?. Strip it for parts and bump it.

Ken de W7ITC