Looks like they are made from some sort of insulating material so used for handeling something at hot or cold temps or something that could be live, something to do with batteries or capacitors perhaps?
1) A tool for parting camel toes or....................
2) Insulated pliers for removing spark plug leads from a RUNNING engine. SUN make a whole range of engine analysers in the States and that may have come as an accesory with the machine but whatever it's pretty vintage! Were they leather or Tufnol?
im gonna guess some sort of marking-cutting tool for cables or pipes.
just dont a load of quick reserch on it from the name and serial num. only found that the company made car test equipment and has been bought by snap on tools.
so based on the extra infomation id guess that it could be used for just about bloody anything lol im gonna guess from that, either for attaching round leads to test equipment or cars or possibly removal of car batt terminals