Radio Development & Research Corp. 500 Get a print! $8.00 Add to Cart Product Information: Model:500 Manufacturer:Radio Development & Research Corp. (Magic Tone) Schematic Pages Page 1 Schematics Content Page 1: MODEL 500 USES LOCTAL TUBES MODEL 501 USES OCTAL TUBES Please note: we carry a wide range of products which will fulfill the specifications above. Please use our search function or browse our products to find what you need!