The Blue Book of Gun Values will give you a ball park. They don't show up often for sale.
Auction Arms has one on its site.
50-150 or so
triplek.com
Old gun catalogs and magazines.
25-100 USD
10-100 usd
50-100 USD
25-100 or so
70
100 or so
-50-300 usd
You need to contact Ruger. You may have a prototype