zignal zero
Well one way to check the value on a particular gun is to sign in on an auction site like gunbroker.com. After you do this, do a search of your Ruger under the category of "Completed Auctions". This will show you if similar guns were sold and what they went for. Then see if anything comes close to your guns description and condition.
You can also get an approximate date as to when your Single Six was built from Ruger's own website, ruger-firearms.com.
There is also rugerforum.net where Ruger collectors may be able to offer some insight and information regarding your revolver.
Without actually seeing your revolver and taking into account its condition, when it was built, and if it's a standard production model; it would probably be in a price range anywhere from $200 to $325.