I can't see the obverse well enough through the toning in the pic on my phone screen to venture a grade opinion, but if it were mine i wouldn't dip it, or remove it from the GSA holder. It's a nice GSA cc with a toned obverse and a semi-prooflike reverse. If they were still going for $200-$250 like they were a few years ago I'd buy it in a heartbeat, with prices as they are now I'd have to think about it for a bit but probably would still buy it.
Looks about 63. On the dipping question, one can never say for sure what the results will be. The toning is a bit unattractive IMHO. It might come out beautiful but you risk devaluing a valuable coin. Sending it in for conservation so an experienced individual does it might be an option too.