I have three WYSE keyboards, one from a Wy-50, one from a WY-30, and a PCE (from '92 if the date stamp on the microcontroller can be believed). The latter two have the 4p4c connectors, and the WY-50 one (number: 840059) has some ancient connector.
I have seen ones like your on ebay, but never bought them. They look even older and weirder than my WY-50 keyboard! Good to see cherry blacks on them, too. Although come to think of it, I suspect it's newer, as the keycaps are thinner.
Gotta love that SP font! Just retr0brite the keycaps, and enjoy.
WYSE keyboards are really great.