very early champion spark plug designed to provide a method of priming the engine on those cold days. I was told 1905 thru 1915.

Those plugs were often used on small single cylinder engines where there was not enough space for a separate primer cup. That was in the era before chokes were understood and perfected. It replaced taking out the plug dripping in a little gas and the replacing the plug prior to attempting to start the engine.

If you look at some of the carburetors of that era they are works of art. Starting from passing air past a pool of gas, to adding wicks to get more gas faster, to aspirating gas into the air flow and then trying to control the mixture at a multitude of air flows took a bunch of ingenuity and trial/error. That discussion should warrant another thread.

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