These look like fired 20mm TP projectiles (hopefully; one example being 20 x 102mm TP, M55A2) that someone recovered some period of time after being fired and then someone used a wire wheel/grinder to remove the corrosion/damage from impact. Most noticeable is the corroded/ground down (inert) aluminum nose fuzes or what is left of them. Probably not a very smart thing to do.
You don’t have to treat them with a wirewheel or grinder to find them in this codition…
This is normal wear on a 20x102 TP when fired into a pile of sand/dirt/debris at the firing range
(left one is range find, fired and untreated, the right one is an unfired “wirewheel-treated” one)
Rotational scratches when the projectile hits the ground can be used to estimate how fast it was still spinning when it went in.
In fact its about the only way they could estimate it years ago. Forward loss in velocity is quite easily determined but the rate of rotation drops off much more slowly over a given distance.
Just to backup orpheus72, here are my range pickups from rocky sandy desert area. No wire wheel was involved.