The early version manuals had a schematic, later versions do not.
Yes, the calibrator has been working all those years.
But I know that there's a internal resistor that will burn out, like a fuse, if the input current is too high, in order to protect the sensing circuit.
So I've continued to look for a schematic in case that ever happens, to be able to know what's what.
I bought a used 1045 for 'parts' that included the 1984 manual and there were the schematics in the manual.