Ted Mahler wrote:
I am not sure how to tell. It is a portable unit (has a handle) and has a
place to put it on a tripod. Its lid folds upright and has the antenna in
it. I believe it was for going into the field and recording signal strength.

Ted

Depending on its frequency range it may be quite valuable, as it
sounds like you have the progenitor to the classic Potomac FIM.They are
$12-15,000 new.