The letter was written, or at least the stationary printed, prior to July 1955. This is based on the telephone number being KIrby 6600. In that month Cincinnati Bell changed from using two letter four digit to two letter five digit numbers. Therefore the number became KIrby 1-6600. The 541 prefix still serves the Northside, Camp Washington (location of Avco-Crosley), and South Cumminsville areas.