From what I can find, the FPU for opcodes starting with 0x66-0x67/0xD8-0xDF corresponds to a uPD72191/uPD72291 (and are different to an x87 which x87 FPU mnemonics in this disassembler are used) as per the HP 64873 V-Series Cross Assembler/Macro Preprocessor Reference (HP Part No. 64783-97007).