These are H-250 “Dog Bone” handsets used in the US Military. The handset uses a 5 pin connector to plug into tactical radios and is not compatible with most radios. The handset is rugged and simple with a easy to use Push To Talk (PTT) on the side. There is a built in clip on the back for attaching to straps for when not in use.
If you are good with electronics there are ways to wire these into connectors for civilian radios such as CB radios!
Does not work on most civilian radios.