Hi Terry,
Its very frustrating to SEE the connector but not to get any damned info on it.

The best I have so far is here.

Data Output and Processing

At present, most digital calipers from China have a data port (SPC) for
data output. The port can be seen by removing a small cap on the slider
(readout head) and can be connected with a PC or a printer for data
processing or for the printing of analytical charts of the measured
figures; via a special cable. The data port is usually termed an adaptor.

Interface working method: Synchronous serial.

Data: Binary code, 24 bits. Each datum will be transferred twice. The cycle
is 300ms (20ms in fast reading state). Transmitting time: 0.5ms.

Four wires (from left to right): Negative power(-), Clock pulse CP, Data D,
Positive Power(+).

Pulse range of data: Level ≤0.2V, Level ≥1.3V

Clock Pulse CP: 90 KHz, effective for high electrical level.


but this ignores "units"

Steve