All I knew is that it was Korean, not Chinese (that is probably why you couldn't ID it.

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Obverse says "Sang Pyong Tong Bo." I'm assuming the reverse needs to be rotated clockwise 90 degrees. The closest thing I come up with is "Pyong" at top (left in the OP's picture, and the numerical character for 11. My reference dates this to 1883 if the size is between 20-23mm.
