Data General terminal keyboard, Fujitsu third generation clicky leaf switches. That seller has been trying to sell it since February and has raised and lowered the price. They have thick double shot ABS caps. What you see in this photo is both the key cap and the under-cap, sort of like a Model M with two piece caps. This is a heavy, metal frame keyboard that cleans up nicely. I have two of them. I don't know what protocol it uses.