That. Ad. Is. Hilarious!
The only way it could possibly be more 80's is if someone was wearing aviator-style sunglasses!
OK, back on topic...
Wow, such a short run. I wonder why they stopped after only 2 years.
The reason is simple: S&W introduced their 3rd-generation centerfire automatic pistols in 1988 and replaced the 2nd-gen M645 with the M4506. (There were no 1st-generation S&W automatics made in .45ACP.)
In fact, S&W curiously built a few hundred so-called "transitional" guns that were marked as a Model 645 but had a 3rd-gen style one-piece wraparound grip unit rather than a separate metal mainspring housing.
FWIW the M645 and the closely related SAO M745 are considered precursors to the 3rd-gen pistols in one respect: they were the only standard-production 2nd-gen pistols built with a pressed-in barrel bushing rather than a separate 1911-style removable bushing. S&W adapted this feature to all 3rd-gen models.
[EDIT: Just noticed that Mr. Cool Dude has said sunglasses hanging from his jacket! Score!