They look like 1098 5-ring pistons.
2.542" is std bore, and 2.562" is +.020" - by your measurements it looks like they are std and +.010" give or take a bit of error.

Many years ago (about 15) I scored two Mini engines from a swap-meet in Sacramento, one was a runner (998) which I put in a Coupé, the other was an unknown pedigree. Every nut, bolt, part, you name it was disassembled in a storage tote, no cylinder head or block for identification just these pistons & con rods.
The four pistons with rods measure 64.61mm diameter and the others 64.81mm, any clue to that block they would fit? I'm not sure how to measure the con rods.
Thanks, Martin.