The Hallicrafters SX-122 and SX-122A were the last "serious" Hallicrafters general coverage receivers. Dual conversion on all bands (unlike some of the competition, which were double conversion on only the upper frequency ranges), 50 KHz IF strip with three bandwidths (5, 2.5 and 0.5 KHz), separate product and envelope detectors, true single signal SSB and CW reception. SX-122 production began in 1964 and ended in 1968.
Hallicrafters Operating and Service Instructions, Four Band Communications Receiver Model SX-122.
"Communications Receivers, The Vacuum Tube Era 1932-1981", 3rd Edition, by Raymond S. Moore
"Shortwave Receivers Past & Present", 2nd Edition, by Fred Osterman
SX-122 photo from the Hallicrafters Collectors Association