"Code Practice Oscillator"
Comment from Philip, K9PL, FISTS #6753: "The Hallicrafters HA/18A CPO in my possession was included in the ARRL's 'Gateway to Amateur Radio' package I purchased in 1976 at Olson Radio in Chicago. The key pictured on your Web site was also part of the package, but it did not include the Hallicrafters packaging. The Hallicrafters CPO was my first step in a 25-plus year journey with Morse visiting its many benefits and joys." Also thanks to Jerry N9DKQ for providing me a copy of the Operating and Service instruction and errata sheets.