A 3-6Mc receiver that I picked up recently has a somewhat odd addition - this a small subchassis that fits over the dynamotor area. It contains a 12SL7 (high-mu dual triode) and a 12SQ7 (dual-diode-triode). There are a couple of pots, and one of the small neon lamps used for input protection. Any ideas what the intended purpose was? 73, ian K3IMW