[Popester]

The feature was called blue sky tuning. KV-1220 had it as it was the more feature rich set with the wood trim and the KV-1210U was the other lower end model without the blue sky tuning feature. When the fine tuning knob was pressed in that’s when the circuit operated and its width would vary with the tuning. I never had that model but was a short lived novelty as it was gone after that model.