[size=12]Circular Dampers saying "New American" and "Reversible Steel Spindle," having p/ns of 14xx or 15xx, and having up to four patent numbers cast into them, are pictured in a Griswold catalog reprint circa 1940 or 1942, I think. Before that, they were just called "American," had only one patent number, and had three digit p/ns of the 5xx form. Before that they weren't reversible - the spindle only went in from one side.
There are also similar-looking dampers that have poorer casting and just say "Patents" without listing patent numbers. They also don't say "Erie" anywhere, and I'm guessing that they were cast after the name was sold.
I sort of collect them, right along with the other Griswold stuff that I collect, but I've become a lot less interested in spending much on them after seeing them go for a buck or two at sales. Some of the older ones that have other kinds of spindle handles than just the standard Alaska coil might bring a little more, and the oval ones or the huge industrial-sized ones (sizes 14, 15, 16, or 18) can fetch nice prices, but plain Jane dampers don't seem to draw a lot of interest.
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