Anyone have a part number for the rotary encoder??

Better question: Can the MK2-style analog-contacts-type rotary encoder be directly replaced with the MK2A-style optical rotary encoder without modifications to the display board?

Sub-question: If Yes, can the optical version of the encoder be ordered with a round shaft instead of a keyed shaft? I happen to like the looks of the round shaft better when used with the backlit knob.