The top (1960A) cabinet is loaded with 4 - Celestion 25w G12M (green back) speakers which all are fine. The bottom (1960B) cabinet is loaded with 4 - Celestion 30W G12H speakers.
This rig has the classic "Marshall Roar". There is no sound quite like this, and in my opinion it cannot be duplicated.
The amplifier has a master volume control, which is a modification. This was on it when I bought it. Since the 1975 models came with a master volume, I can only speculate that the person that added the master volume did so after this came as a stock option from 1975 on.
Jeff Roe
Here's the link:
http://www.thepitchergroup.com/eBay/Marshall



