Auction sites, estate sales, gun stores, sporting goods stores, newspaper for sale ads, etc..
Ruger's website has a sn fucntion that allows you to find out when a firearm was made.
Ruger's web site has sn data.
1970
about $500
100-1000
1975
They can run from 100-1000 or so
Ruger has sn data on theri web site.
61-85
Check Auction Arms, Gun Broker, or just do a web search
For sale ad, on line auciton, place a want ad.
i found a rifle named that. that is listed for 600$