cayugad
I have those same sabots. They were indeed Harvesters. At one time Harvester even made TC's Red sabot for their Mag express sabot. I think the real key is Harvester's have a small plastic tit in the center of the cup. MMP smooth cups are exactly that smooth from rim to rim. MMP 44/50 on the left and Harvester 44/50 on the right. These are the current sabots.
They are very comparable to the size of the current regular Harvester or HPH-24
Think I might have a picture... gotta go look. But, they will be the older polymere. Well I found the picture... it is about as old as the sabots so you really do not get to see much... Worst part I still have some of most of these...