You guys beat me to it.Actually the M-77's with the tang safety's were made from 1968-92.The "All Weather" MKII was introduced in 1990.The revised M-77 known as the MKII was introduced in 1989.If you want to know when any Ruger was manfactured go to the Ruger site.It gives years mfg by models and serial numbers.
www.ruger-firearms.com
Ruger Redhawk