On the Planet unit, ,,,,,i would touch it, it looks very orginal the way it is. If im seeing it right you have one good one and a parts one right?
I have a #4 here with 2 star wheels, but i never use it, as its only half the seeder that the 300A is. I have 2 300A's, and at one time had a Planet frame work that fit the rear of a JD "L" tractor, that was 3 rows of 300's with marker arms. I traded it to my brother one time for something else i thought i needed at the time. Those star wheels are double side on mine, you turn it over to get another drill spacing, ie, the 6 will do 3 or the back side and the 4 will do 2. Also the #4 is the same as a #25, both are set to use as a wheel hoe with a single or double front wheel, and a lot of tooling for slicing and dicing any weed. I think the #25 is more of a commerical unit, like the 300A was.
On the other seeder, I know what it is but cant think of the name right off. It might be a Standard or an Acme, but i'll have to look it up this weekend. You could just send it out here and ill do a 5 yr trial and test on it, lol. Nice lid you made on that one.