1966 Washington Quarter - Rim Error Reverse?

Nope.

 

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As others have said a "folded over rim." During the planchet upsetting process there was a small burr on the edge from the punching out process and the upsetting mill pushed it over one side of the planchet where it was then struck into the coin. During circulation it partly detached from the coin and raised up a bit. A legitimate mint error but unfortunately not a significant one.

 

I forget what you call it, but I believe it was caused during the strike. On the Obv note the extra thickness of the rim above LIBERTY, the weakness of the rim ENE of the Bust and SW of TRUST, and the cut-in of the rim below the DATE. On the Rev note the opposite of those attributes on the corresponding sections of the rim including the cut-in below QUARTER DOLLAR. Just my observations of the OPs photos.
Semper Fidelis and Merry Christmas

PS: I should have said in the up-setting process (as noted by CaptHenway) and from the strike, but I didn't consider the former until after I saw his post.)