Typically, these 2 x 15 big-box Bassman cabs would be seen with CTS, Utah, or Oxford speakers, with JBL D140F's as an extra-cost factory upgrade. Utah speakers would usually be found with orange-and-silver labels, the CTS and Oxford speakers often with none at all. All may be ID'd by a correct interpretation of the EIA codes ink-stamped on the frame basket or magnet assembly.
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY