R4 controls the output impedance of TR1. It'd have to be high to keep the loaded Q of the L2 tank high. R10 looks like a mistake to me. Probably should be 390 o

R4 controls the output impedance of TR1. It'd have to be high to keep the loaded Q of the L2 tank high. R10 looks like a mistake to me. Probably should be 390 ohms. Agree with your assertions though. It might have been reverse engineered from something badly or drawn up by someone smoking crack. Even Tektronix had that problem on occasions in their service manuals ...