Pics of two 4120s added on this page – serial number 235, which is new. Thanks to Tim. And an amp that spent a good deal of its working life in Wales paired with a Super Foundation Bass cab (towards the foot of the page, among the amps with missing serial plates, or numbers simply unknown).
Old pics of 213 have been now been matched up with a newer set showing the serial number.
Ten 4120s in total are currently known. It seems likely that others will surface.