Question: are ignition condensers voltage specific?
Answer: No such thing as a 6V or 12V ignition condenser. Irrespective of applied primary voltage (6V, 12V, 24V) the condensers are made to withstand the flyback or reverse EMF voltage made by the coil as it's magnetic field collapses when the points open. That is ~80-100 volts for a typical iron core type ignition coil.