The Imico System was a rare vapor heating system. "There is no air valve at the radiators in this system and no trap on the return end of the individual radiator. Vacuum is maintained in this system by the Dewey tri-duty air and vacuum trap, which is a combination of the Dewey quick vent air valve and the Dewey vacuum valve." Here is some information about it from The Heating and Ventilating Magazine.
This document contains the complete illustrated instructions for installing the Hercules Steam and Hot Water Heating System, a boiler manufactured by Sears, Roebuck and C...
This document contains the manufacturer's instructions for the HB Smith Series M450L Mills Water-Tube Boiler for automatic firing with oil or gas (Steam, Vapor, or Water ...
This document contains the jacket assembly instructions for the HB Smith Series 45 Mills Boiler (circa 1979).