No Date Washington Quarter Cud?

Now I see well the variety you has. You has sure RDV-006 which run from1967 till 1972 inclusive. I have no doubt of.

That is a GREAT edge on image!! it shows the Cud rising up above the obverse design elements, and the reverse in the same area is lifted a little due to the lack of pressure.

I would start off slow with 5-10 mins and see how it affects "the green". Then longer if you see some improvement.

Fresh acetone each time and a final rinse with distilled or filtered water.

I saw also the side (reeds) has green. The acetone will not do the job. In fact in artifact restoration the acetone is never use. Your green come from the Cu and not from Ni oxide. To clean this other solutes or procedures must be employ with the consideration of the Ni presence. If was just Cu coin I was put you (send private) the table of procedures and what could be use.

The most simple way if you has the equipment (because the green is in the early phases) is boil in 35% boric acid for 3 to 5 min, then in an dark room apply 240-280 nm UV at 60 deg C solute for 2 min. Took the coin out, wash with boric mild soap (baby soap) in warm water and dry without fronting. Mention in the boiling and UV apply procedure the coin must be suspend ( I use big cheese tissue).

Good luck, Silvio