There is a big difference there, that G12H-55 has the low frequency cone in it, and a reproduction of the original voice coil and coil former.i think the "G12-C" has a larger magnet than this one, which is 20 oz, and ceramic
also, this has a 1.25" voice coil.
i have a Heritage G12H-55, and side by side these sound nothing alike.
my old greenback sounds completely different as well.