hap will complement my answer, because I tend to complicate explanations.
But let's see...

Unlike Sapphire-II/Diamond-II where the MCU is identical, not similar but identical, in Sapphire and Diamond we have that the MCU is the same type (H8/3258) but different packaging.

Sapphire has 6433258B46F (QFP package, ROM serial "B46") and Diamond 6433258B47P (DIP package, ROM serial "B47"). This "ROM serial" difference may be due just to the difference in packaging, and that the ROM is the same or, even if it has some small difference, it is in practice the same. But to know this, we will also need to dump Diamond's ROM.

Besides, I understand that there is a Diamond at 20MHz instead of 26.6MHz and therefore a different MCU. This is also being investigated.