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.
The Improved Webster Type "R" System of Steam Heating is a service bulletin from Warren Webster and Company (The Pioneers of Vacuum Steam Heating), established in 1888.
This manual was created by O-E Specialty Manufacturing Co. and outlines how to install the "O-E" Perfect System, which is a Vapor Vacuum heating system.
Here is the original Installation and Operating Instructions and Parts List for The H.B. Smith Company's Oil Fired Cast Iron Hot Water Boilers (No. OHB-13W). This is esti...