If that is not the same, there may not be a schematic available.
Sams only lists a 611, in folder 329,(which dates it to about 1956/1957) but the S.C. model Idents leave a bit to be desired.
Short of extrapolating a date from the patent sheet, you would need to base an estimate on the tube complement and the overall appearance of the unit.
: I am trying to restore a Setchell-Carlson 613B amplifier. Does anyone have a schematic or other information about this amplifier (such as when it was made, etc). All help appreciated!