The CTC13 is an experimental set that consists of a modified CTC12 and a developmental 90-degree round CRT from the RCA tube plant in Lancaster, PA. Although no documentation surrounding this set is known to have survived, including a schematic, a Lancaster-based RCA engineer familiar with the set reported that only four of these sets were made. This still-operational chassis is scheduled to undergo restoration in the spring of 2007 along with cataract removal from the developmental CRT. Amazingly, the set includes a spare CRT; it is marked with a 'tested OK' on its carton, dated September 6, 1974. It too requires cataract removal. A rare set indeed.