Looking at O&R stuff on the net, one bloke says that these engines only lasted about 100 hours, so don't use it, just look at it. Others are less unkind and actually use theirs.
From a brochure I just received:
AMP-CHAMP is a product of more than sixteen years' experience gained as a major supplier of power sources and related products to the military and industry.
AMP-CHAMP will run hand drills (3/4" in steel) and most other small tools and appliances. Light and powerful. Has AC and DC outlets. In addition, Amp-Champ will charge 6 and 12 volt auto batteries and run 12 volt auto accessories.
AMP-CHAMP will light three hundred-watt light bulbs, power table radios. and power spolights and radio transmitters.
MODEL CP100: 240V AC High Cycle. 240V AC/DC. 350 watts.
RELIABLE: Brushless flux switch alternator-no commutator problems.
Engine production seems to have been in the 1960s - 70s era.
Eric