[Eliot Ness]

Gloritone, US Apex, and Radiotrope were all made by U.S. Radio and Television Corporation in Marion, IN, so the same chassis may have been used in different models, but only one of those, Apex in your case, showing up in Riders.

A prefix was used on early tubes to indicate the manufacturer.  The most common examples are RCA and Cunningham that used a 2 or 3, so a Cunningham would be a 380 and RCA a 280. Typically the globe style tubes used the prefix which was dropped when the newer ST style tubes came out.  Your 80 is just a later version of a 280 and is interchangeable.