I have one almost like it. There are a few variations.
It is a keyboard for Digital Eqiupments (DEC) terminals. Not PC-compatible.
Hard, mushy rubber dome. Spherical key caps.
I hope that you did not pay much for yours.
Actually, you can quite happily use these on a PC via the PS/2 keyboard port.
Software like WRQ Reflection can be used with a custom keyboard driver, otherwise it will function as a PC keyboard.
Didn't like reading the price you paid mind, I just spent more than that on one. It is brand new mind, but they are pretty rare now.
The layout is for the OpenVMS operating system. The legends on the front of the keycaps are for a fairly ancient word processor called WPS-PLUS.
It was also built into an Office Productivity package called ALLIN1.
If you have no use for it let me know - I could always use a spare!
Regards, Mark.