[Ron Ramirez]

I believe those electrolytic rectifiers used a boric acid solution(?) - nothing too exotic...

+1. I recall reading something about this about 100 years ago, back when I was just getting started in this hobby, in Jim Fred's Antique Radio Corner column in Elementary Electronics magazine. I do distinctly remember a boric acid solution being mentioned then; basically the same solution as used in the older Mershon, and later aluminum can, wet electrolytic capacitors. I have read the same thing elsewhere since then.

Now, regarding the car radio: If the model number ends with the letter P (I can't really tell in the photo, but it appears to), then it was made for police use. Which means Bill (exray) is right on the money.