I'm going to vote for dibbers. The one on the right may be a worn down plank hook, but the one on the left looks like it has a wider piece on the end.
The way the handle is on the top, would lend it self to walking up the row, and pressing your foot on the metal bit sticking out the side. But the footplate bit looks to long, you'd be catching it against your other foot, and it doesn't need to be that long, or have an up turn on it.
And any way, if the ground is so hard you need to put your foot square on it to make a hole to put a seed in, then you've got a problem.........
I think I've just managed to convince my self that they aren't dibbers.........