Hey, I knew I wasn't remembering this wrong!

note the car player and the home players.

Man, looking at Billboards from the 1967-68 timeframe, you can see what a big deal the cassette 
launch was to the business. Philips played the whole thing very well.

Also in the above-linked Billboard, check out the profile of the Walthamstow, England cassette 
duping plant. That would be one of the early ones. At Fine Recording, they would dupe many copies of 
a tape onto a 10" NAB reel of cassette tape, at 16X (yes, cringe-worthy fidelity was achieved). 
There were tones encoded at the place where the tape was to be cut. Then there were loading jigs 
where one of the  ladies (they were all female doing these jobs) would splice the head of a single 
cassette into the shell, run the machine which would fast-wind the tape and then cut it in an action 
initiated by the end-of-program tone. She would then splice in the other end and put that tape in a 
case as the machine loaded the next. There was a similar process for 8-track and 4-track cartridges. 
I think there were also cassette-loading jigs where the tape was physically atached to the spindle, 
the spindle wound at fast speed and cut and the other end of tape attached to the other spindle, 
then the shell screwed together. I don't think that was common, though, be cause it took much more 
skill than simply making splices and letting the cassette load into its own shell.

-- Tom Fine