Only 3 1991-P quarters have sold on Heritage based on their auction archive. However, all were PCGS MS66. Here are those prices and dates: 5/2/2010: $47.00 11/14/2007: $89.70 2/27/2007: $74.75 They also have an NGC MS67PL that sold listed too, it was sold on 4/16/2006 for $80.50. So, that should give you a basic idea. Based on those prices, I would say that the going rate for your coin today would probably be around $40 or so.
The NGC Census lists 28 @ 66 with 23 @ 66PL or better. Numismedia lists the value of MS66 @ $52.50 Chris
I'll say. One recently sold on eBay for $18.50. http://www.ebay.com/itm/1991-P-Wash...74?pt=Coins_US_Individual&hash=item35b442479a
