Over the 55+ years of production of the Triplett 310, the probe design changed considerably. Probes grew in length and girth, I suspect largely in response to changing safety regulations. A finger-guard was added as well as provision for attaching alligator clips to the probe tips. Pix 1, right to left, shows the progression of probe designs. I
can't imagine holding the tiny probes on the right to measure 1200 VAC, the highest full scale reading available on the standard 310.
To accommodate the larger probes and added alligator clips, unfortunately the carrying case for the 310s had to grow to larger, fatter designs. Pix 2.
I mentioned in an earlier post that
even though the very early 310s did
not have a provision for attaching the clamp-on Amp meter probe, the ground receptacle on the top of the meter case served a useful function. The design of the early probe set allowed the negative probe tip to be unplugged from the probe body as shown in Pix 3.
The banana plug from the probe tip could then be plugged into the receptacle on the meter to provide a convenient method of probing a chassis. Pix 4.
jr