Just a note of caution about the early SC2 compressors….. The LDRs (Light Dependent Resistors) used to produce the compression do have delicate termination wires and can break. The cells can also deteriorate eventually (although I’m using some that have been in service for nearly 50 years… so they are not that bad!)
The electronics in these compressors is quite basic and rugged and the most likely cause of any defect is the gain cells (LDRs)
L/R gain differences are often noted and these are caused generally by inequalities in the tracks on the gain controls, usually the input gain control. 
