Packless radiator supply valves kept air from working its way into a vacuum system. This bulletin from C.A. Dunham Co. is from 1916 and features the Dunham Packless Inlet Valve. Thanks to David Cordes for sharing.
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...