See if it's here http://www.okiegunsmithshop.com/lvl25.html He has exploded views of many, many firearms...
You need to contact Ruger. You may have a prototype
Ruger's website has serial number data on its products.
Ruger Single Six
Ruger's website lists the current offerings.
RUGER PISTOLS ARE GOOD GUNS, ABOUT $600
50-165 or so
50-175 USD
If Ruger's website is up, they have extensive sn data on it.
100-400 USD
Browning, Colt, Ruger, Smith and Wesson, Walther, Hammerli
The numbers 10-21133 are the serial number that was assigned to your Ruger Standard Mark I pistol,which was made in the year 1969.
Email or call Ruger Customer Service. There have been issues reported with their published SN data.