Those speakers are basically early E120’s made for Fender. Do they have the original aluminum dust caps in good condition? If so, heck of a deal.
For what it’s worth…the original 12” JBL was the D-123. When JBL started working with Fender, they made some minor changes and they became the D120F in the early 60’s. The D120F had a large Alnico magnet, cast frame, 4” edge sound voice coil, aluminum dust cap and a treated paper surround (D123’s may have been untreated paper surround).
Around 1973/74 JBL upgraded the D120 to the K120 which had a treated fabric surround and better longevity and power handling. What throws a LOT of people off is Fender chose not to use the new name, so through much of the 70’s Fender was selling amps with K120’s labeled as D120F, many of these had the orange frame vs the earlier grey frames but they are otherwise identical to a K120 or a D120F that was reconed with the fabric surround K cones as many were.
As Alnico became very expensive in the late 70’s, JBL developed the ceramic E series including the E120. These speakers weighed even more than their predecessors but also had even higher power handling. The speakers you have were early E120’s with Fender labels and a different part number, but I believe otherwise are identical or extremely similar to an E120.
They are going to be very efficient (loud per watt) and can handle a ton of power to get very loud. They are best for clean to moderate distortion, have a more extended frequency range than many guitar oriented 12” speakers, and a somewhat distinctive JBL sound that was favored by many at the time. JBL’s were an expensive upgrade to Fender amps, but popular with pro’s due to the sound, output level, and their robustness/power handling. Think Freddie King, Jerry Garcia, Alman Brothers, and early EVH among many others.
As for the amp, hard to tell, but based on the speakers, I am guessing it is a late SF with the 135w UL transformer. They are not as desirable as the BF or earlier SF for those who want to overdrive the amp and get a little dirt, but they are sought after by pedal steel guys and others looking for clean headroom for days. Especially with those speakers, it will be loud and clean. Like loud enough to cut over a 100w Marshall full stack!