I did see that article in Farm Collector. I'm going to see if I can get a hold of him to see if he has any owners or operators manuals for it he might part with or be willing to make a copy of for me.
I've been looking it over and freeing everything up the past couple days and think I figured out how it works and got some pictures of it
There's a rod that runs up to the handle that you pull which moves the arm with the spring up and pulls the tab that the pencil is pointing to down. This turns it on and allows everything to move.
With the lever pulled it lets the arm in the top of this pic ride on the wavy ridge on the inside of the wheel.
Closed so no seed can get out.
All the way open with the arm that rides on the wheel on a high spot. Pencil is pointing to a ridge on the plate that shakes the seed down.
Another open with the arm on a low spot. Ridge is offset. The spring in the top of the pic keeps tension on the plate to bring the ridge back to the middle as the wheel turns.
Looks like it's pretty simple to operate so hopefully it goes good for my dad when he uses it.
I managed to get the info tag that tells you how far to move plate forward for what seed cleaned up. It doesn't list corn but when its all the way open is for planting peas so that should work with the corn seeds. It lists turnip, celery, onion, radish, parsnip,carrot, spinach, beet, salsify, beans, and peas for the seeds