1966 old model .357 blackhawk value?

I recently was given my grandfathers old model .357 magnum Blackhawk. I've been doing some research on its value. I spoke to Ruger and learned it was produced in July 1966. I'm trying to get a ballpark value on it.

Details:
serial # 8002#
old model / 3 screw
has "Sturm, Ruger & Co., Inc. Southport, Conn. USA stamped on barrel
4 5/8 barrel
blued
NOT SAFETY UPDATED/MODIFIED
walnut grips
rarely ever used, has been boxed and stored for last 30 years
overall excellent condition

Thanks for any info you might have.

hello,,i'd say your grandfathers blackhawk in the condition stated would be valued at between 500-700,,at auction or to a ruger collector,,dealers would proably be in the 275-350 range for a trade in or purchase price,,
bigcurt