The serial number indicates it was made in 1966, with the "diamond" in the grip going away the next year. The Model 36, the patriarch of a large line of J-frames, was discontinued in 1999. The new designs carry the old model numbers, to some extent, but are vastly different internally, and externally.
As with anything good that arrives via time machine, the previous owner kept everything intact, and may not even have fired it.
I noticed a light coating of rust on the trigger rebound spring when I removed the grips, so I will open the revolver up (I've done dozens of S&W J, K, L, and N-frames, and they're identical internally), and replace the little coil springs with new ones. It will no longer be pristine untouched-original internally, but nobody knew then, or now, how to guarantee fifty years of perfect spring life. A few dollars of new springs, identical to the ones used back then, will leave this unfired safe princess ready for another almost-fifty years of pampered luxury, but still ready to roll into action instantly, if needs arise.
I had no idea this gun was in the display case, but it was so pretty, just based on age, condition, and sterling reputation, that I had to buy it just so it could continue to be pampered. Another owner might have done the same thing, or maybe not. But like a puppy from an animal shelter, I can at least rest easy knowing this one will be well cared-for.