priced per ring

135 Bcd

brand new rings, removed from campagnolo 10 speed Veloce cranks 

the bigger rings are matched to go with the smaller - (the matching only affects only the big one) - you should a big ring that's matched to the small ring size, 

The small ring doesn't have any special differences, so can go with any bigger ring as long as that bigger ring is matched to go with a 39t

- these say 53/39 on the large ring so are optimized to shift up and down from a 39t inner ring. a mix and match will still work, especially on friction but ideally the smaller ring should match what's said on the larger ring. 

As for the "MPS" i think that just refers to some small improvements in the lifting/dropping technology - pins, ramps, shaped teeth etc.