I got to reading all this "jack stuff" so I pulled the one in my to be done pile and did a bit of closer inspection. This one came from a collection of 65 and 66 parts so it's almost off topic. There does not to appear to be a date code stamp like the one Marcus has but it does have the paper instruction label, faded to nothing. It does have a tiny bit paint on the teflon washer and possibly some on the drive screw. The configuration is a combination of the top and bottom jacks in Bob's first picture, the drive screw ends are like the bottom jack into a block, the saddle is like the top jack, just a dip. What caught my eye is the drive screw. It is a double square cut thread - get that, double cut thread. If somebody is ambitious, would they check theirs for this type of thread. I used a black Sharpie felt tip pen placed on a thread and turned the drive screw a couple of full turns. It skips a thread.
Jim