I had a factory JBL equipped twin for a very short time. Get the best sound for music, smartphones, tablets & TVs with JBL. Premium speakers from JBL such as wireless bluetooth speakers, Android & iOS headphones, soundbars, subwoofers, home theater systems, computer speakers, & iPod/iPhone docks. Genuine JBL Products will have a serial number that can be successfully registered. Is there some way to identify genuine JBL speakers. JBL's are universally considered 'hi-fi'.very clean, good bass but perhaps a bit harsh on the treble side.brittle maybe?
Another clue on a later 60's speaker might be a tiny F punched into the foil label.
Unfortunately these stamps are not always on the speakers and are sometimes on the cabinet, or on the inside or outside of the chassis. Supposedly, if they are original to that amp, they would have an ink stamp on them that matches the stamp on the tube chart inside the cabinet.or a stamp that would be a code like AA2565.25th week of 1965. Hi Scott, It is kind of rare to find factory installed JBL 120F's in a twin but not unheard of.