I believe the 1st and 2nd were a bit piecemeal, with mahogany core but maple veneer tops. The 3rd run, while lacking the tummy contour and a bit thicker than the others, they were solid mahogany, and pretty nice pieces at that.
Having not played an original NR, just the earlier reverses, I can't say I have that much of a basis of comparison, but I'm a bit surprised there's that much of a difference between the Bachs and the originals, as they were supposed to be based off measurements taken from the originals, although I knew there were some differences.