No die shots but the Wikipedia articles of all things on the MK61 and MK52 are surprisingly thorough including photos of the PCBs, schematics, and the External Links sections contain most of the interesting articles I'm aware of about these.
They're quite interesting and quirky machines, definitely HP-inspired but unique in a lot of ways. Especially the MK52 with the built in EEPROM (though other than the EEPROM and connector for an external ROM it is functionally identical to the MK61). They're also still readily available and cheap on eBay if you want to play with one.