It's a DP-100 Digital Video Probe in mint condition. It works in TM500 or TM5000 frames. I don't have a P6454 or P6460 to go with it, but I see that QService currently has a P6460 available.
"The DP-100 Digital Video Probe provides an easy way to observe up to 10 digital data lines simultaneously ... Output can be displayed on a picture monitor, waveform monitor, vectorscope, or an oscilloscope"
I'm open to offers on this as while it's apparently a bit rare, it probably also has limited application.
Cheers
Dave
David C. Partridge