That serial number falls in between 1981 and 1982 on Rugers' serial number chart. I would guess it was manufactured somewhere in between those 2 dates. I think the only way you may be able to find out quickly is by calling Ruger 603-865-2424.
Here is the link to the Ruger Security-Six .357 Manufacture Dates
Ruger Security Six, Single Six, Service Six Serial Number History