These Early 1970's Sears Amps fly way below the radar. These were the last tube amps sold by Sears and they are pretty darn awesome vintage bang for the buck.
This model uses a 7189 Output tube and 12AX7 Preamp which is basically the same as a Vox AC4.
The trick with these 10XL's is to look for the ones with the "square red power indicator light." I know we are really nitpicking now but apparently they alrered the circuit at some point when they also switched the red lens to a round shape and it didn't sound as good (or so I've heard).
Here is a website called Tonegems that tells you all about this model: http://www.tonegems.com/silvertone-1421/