Nice box you scored there! This is really pretty good gear.
Is this device PAL or NTSC labeled somewhere?
I spent a part of my life in broadcast TV env, so regarding some terms:
* I think the D1/D2 stand for digital video stream, in D1 or D2 type, which basically is composite or component, I do not remember the exact numbers for the D's.
* A "key" video is a video you use to cut, think of it as a transparency mask, which can use only Y, or the chroma part (called chroma key then)
Sony in those days manufactured (maybe still today) a lot of video/audio handling chips, from ADC/DAC, conversion, mixing, etc. Other manufacturers used them. I have seen Sony ADC/DAC and composite/component conversion chips in Panasonic DVCPro devices.
Pretty interesting you found datasheets for the mixing elements like the the "component to composite digital converter" (CXD8063), "to channel video mixer" (8062), "polar coordinate" (8060).
One interesting block I saw was the float integer one.