since a few days I am experimenting to use NCo library in the context of COM. But as far as I can see it is not possible to do that, because the sapnco.dll and sapnco_util.dll are both market with <Assembly: ComVisible(False)> attribute. Both are version 22.214.171.124 and this applies for x86 and x64 architecture. You can find more information about ComVisible here and here. If you want to register one of the libraries via regasm, with the parameters tlb and codebase, you will get the error message No types were registered. What a pity. If it is technically possible, the provision of this libraries could create new horizons for this kind of requirements.
Here the difference of the IL code:
.custom instance void [mscorlib]System.Runtime.InteropServices.ComVisibleAttribute::.ctor(bool) = ( 01 00 00 00 00 )
.custom instance void [mscorlib]System.Runtime.InteropServices.ComVisibleAttribute::.ctor(bool) = ( 01 00 01 00 00 )