Posted by JasonB on 04/12/2021 17:56:23:
Yes it's a lubricator based on one on an existing engine. The lever cock is on/off and the tee handle adjusts the flow
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The type can also be refilled without stopping the engine, which was important when they worked long hours for a living. (Rather than being steamed in short bursts for display or turned over with an electric motor.)
In operation the lubricator is under pressure and simply removing the top is liable to blast out oily steam. Temporarily closing the lower cock allows the top to be removed for safe refilling. Doesn't take long and the engine can be kept running.
Dave