So I was given a free pair of (what seem to look old) ADM 1540 equalizers today and I'm very unfamiliar with the product. I am not finding much info online. The ones I'm seeing online have the actual number "1540" engraved next to "ADM" but mine do not. I attached a photo. Any info on worth or the year it was made would be great. I've attached a photo. *** bonus points. Where could I get these fixed up?