Build 12208, this is still coming up as an unknown item. (It has been for a while, I just kept forgetting to look and see until now if this had actually been added. >.<) From the CLI:
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Looking at item #3840...
Unknown item found: anniversary tiny latex mask (3840, 458954233)
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3840 anniversary tiny latex mask 458954233 tinymask.gif familiar 0
anniversary tiny latex mask Familiar Weight: +1