Just got this one off of ebay, a '56 RCA 8BT10K 7 transistor AM radio. This one is built on a metal chassis with socketed transistors, which I especially like. It also uses an oddball battery that's a new one on me. The RCA battery number is VS301, which is a 9V battery pack with a 3V tap. Since this battery probably hasn't been made in 40 years, I'll have to make up something using modern batteries. One major problem is that the knobs are disintegrating and coming apart with missing pieces where they slide over the control shaft. One knob had already been glued back together and I had to glue the other knob. They are staying on the shafts; but, I don't think they'd take very much abuse. I connected the radio to two power supplies to get the -3 and -9 volts; and, it seems to play OK.