Justin, Although the lens elements maybe of the same design.e.g. plano-convex;plano-concave,etc and both lenses consists of 6 elements in 4 groups, "Refractive Index" is a property of the glass manufacture. As these glasses (Leitz vs Minolta) come from 2 different factories, it is unlikely that their R.I's are the same.Their individual performance may well appear similar.
Colin
Colin