Any clue what this is ?

Hey, I bought this from the flea market today without having any idea what its purpose is. When I first looked at it I thought it was a home made siren or some kind of effect. The plug on the left looked like XLR but when I arrived at home I realized that it’s a little bit smaller, the other black and red plugs look to me like the ones you can find on oscilloscopes so it may be a voltmeter or something like this. If any of you have a clue of what this could bi I would appreciate the help and sorry if it’s not the right sub to ask these kind of questions