Carbon Pile Load Tester

Hi together,

I am looking for a high current load tester and stumbled over carbon pile load testers as for instance the DHC500A2.
Does anyone know which carbon pile resistor element is actually used in this load tester and whether it is available separately?
Or does anyone have a picture of the inside of such a tester?

Thanks,
Philipp

It's basically a stack of carbon (graphite) blocks which are pressed together with more or less force in relation with the wanted resistance and therefore the test current.

The force can be applied via a screw:


Or for regulation purposes via a spring counteracted by an electromagnet:



It's a very very old technology, pretty imprecise but very robust.