Yes, the 24/2.8 K (last pre-AI version) is optically the same as the N-C version, with 9 elements in 7 groups, fully multicoated. The K version is a bit nicer though, it has 7 aperture blades compared to 6 for the older versions, which I think gives nicer shaped out of focus blurs. It also stops down to f22 instead of f16 for the older versions, if you need to stop down that far.
The optics changed with the AI version to 9 elements in 9 groups, in a slightly more compact design. The same optics went essentially unchanged to the AIS, AF and AFD versions.