It's a crypto interface and crew terminal from a military radio system. It isn't useful on its own, and a lot of equipment of this nature is not legal for civilians to buy or sell. That said, this isn't the first time I've seen that exact terminal pop up in ham radio forums, so I suspect it's a model not covered by current control policies, though I can't guarantee that.
There's no RF deck, it's essentially a remote control panel for a radio that would just be an enormous green box with handles and connectors on it. The buttons around the edge of the screen are multi-function keys, and on most of these, new crypto can be pushed through the headset connector using one of several different kinds of loaders. Similar units are used on aircraft for both radio and intercom systems, but I suspect this one is from either a fixed station or a modular mobile unit, as it doesn't have a plate where it would seat in a console or the like.