Thank you, Sannazay, for your assessment. After posting my previous message and thinking more about that sticker, I agree with you that my machine is a 1979 vintage. What threw me off track initially were other messages I had seen that said Hobart had dropped "Manufacturing" from their name in 1974. Either that was incorrect information or my machine was constructed from parts that were remaining in inventory five years after the name change, specifically the locking plate (AKA screw cap kit).
Reinterpreting that sticker without considering the name change leads me to believe that my K45 was made on day 173, or June 22, of 1979. Thus it could indeed have been one of the last of the K45 models to be assembled. I tried to look up the date on which the assembly line switched over to building the K45SS model but couldn't come up with anything.
Incidentally, you were correct about the attachment hub cap having been replaced. It was missing when I acquired the machine from the son of the original owner and I didn't like looking at the gaping hole in the housing. Perhaps I should have bought an original, unadorned cap from someone on eBay, but the one with the KA logo looks very contemporary.
My new Artisan 5 qt. (KSM150OB) is nice and all, but I'm really cheesed off that Whirlpool decided the spring-and-washer assembly on the "agitator" shaft was superfluous and eliminated it sometime around 2016. Without that spring, the flat beater/dough hook/whisk attachment doesn't snap on with authority, thus forcing the user to look to make sure the attachment really is engaged. The original Hobart design showed great attention to detail, the subtlety of which seems to escape the Whirlpool engineers.
You can't buy those parts from Whirlpool parts retailers anymore, so I had to order them individually from other sources so I could "upgrade" my machine to original specs. I couldn't order just one spring and one washer, so I ordered the smallest quantity of each that I could order. I may end up combining the surplus pieces as kits and selling them on eBay for anyone who wants to make their machine whole again. Pulling that planetary assembly is so simple that anyone with a modicum of mechanical ability would be able to install the kit easily.
Over the next week or so I will be cleaning out and repacking the gear grease on my K45 -- using genuine Benalene 930-2 grease, of course. One has to be very careful if using ordinary food-grade grease, as the temperature profile might be completely different.
I haven't decided yet whether to keep the K45 or to sell it to someone who can give it a good home. It is in really great shape but, to be truthful, I really don't have the space to keep two KitchenAid mixers. If I do keep it, however, I might upgrade it to electronic motor control. (The last I knew, America's Test Kitchen still rated the 4.5 qt. KitchenAid mixers as their "Best Buy" in consumer stand mixers.)
