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This is probably the earliest outdoor reset control. They lasted a long time! The brochure is from 1943.

This is one of the first attempts to move the attic expansion tank in a gravity hot water heating system to the basement. Thanks to Alex Marx for doing the scan for us.

This brochure from Taco Heaters, Inc. was published in 1953 and showcases Taco heating products such as circulators, flow checks, venturi fittings, the Taco paneltrol, Ta...

This circa-1950 brochure features Radiator Heat Plus Taco-Trol for Hot Water Heating Systems from Taco Heaters, Inc. It reads, "The Taco-Trol is a combination hot water h...

This is a patent that Gil Carlson received for a drain and vacuum breaker valve in 1957.

Honeywell tells the story of their Aquastat in this document. It is not dated, but is probably from the 1950s.

Here is a 1909 patent for an unusual, and very creative, regulator from J.M. Dougherty & H.C. Tabler.

The Honeywell Air-Seal Generator is a turn-of-the-century offering from Honeywell. It is similar to their Heat Generator. Thanks to Alex Marx for scanning this brochure f...

After moving the gravity-hot-water-system expansion tank from the attic to the basement, The Stack Heater Company introduced a heating system that didn't need a tank at a...

Here instructions for the Thrush Flow Control Valve from the H.A. Thrush & Company. Thanks to Mike Zydiak for finding and sharing this document with us.