according to the datasheet i was able to locate, these may be 250ns, as the 4 (in 54) may refer to the speed (2=150, 3=200, 4=250, unless of course the 5 = 300...but it wasn't absolutely clear on that), that is about all I could find. (they were probably also made in the 19th week of 1980)
also ITT made a few things, including Apple II clones (which i presume they used these in as well)