I have found very little about this piece. Made by Marti Electronics it is a model 25C, I believe it is a transmitter. The tag also reads M-25C / MR-30 / 150-170. 15 vacuum tubes in the unit. All look to be original vintage, I see many of the Bugle boy ones installed. It has a Turner Carbon Microphone attached. This came from a local radio station. This unit was hooked up on a rack mount. Now I have no way to test so I have to sell it as I found it. Pretty cool old piece. Please check over the photos. Thank you for looking.