Test and Maintenance tools for vintage computers

My interest in vintage hardware certainly includes acquiring and restoring the hardware itself, getting copies (or originals if possible) of the manuals and other documentation, but also includes acquiring the original "tools" and other articles used to keep these old systems running. For example, I have several teletypes of various models, and Teletype corp was fond of having all sorts of special tools used to keep these things running smoothly. Items included special screwdrivers, burnishing tools for cleaning contacts and even a custom "tuning fork" for aligning the speed of the governored motor. I recall, for example, that our DEC field service engineer at Oregon State had a special "tuned hammer" for "thwacking" the circuit boards in our PDP-8 (straight-8) that ran our front-end terminal multiplexor. Basically it was a modified "center punch" with a special paddle in place of the sharp-pointy thing. You dialed in the amount of "thump" desired (in special DEC-calibrated units: (1-light to 9-break-the-edge-fingers) and pressed the tool against the card handle, pushing until the center-punch device clicked. All boards were supposed to take at least a "4" if I recall (any DEC FE's out there?) and any that didn't were replaced. So, what's the strangest "field service" tool out there? And what success have you all had in finding these things? For my teletypes, it's been a difficult task to find the pieces I have and I only have a few of the 30-some "official" tools TTY-corp produced for the model 14, 19 and 28 families. Seem to be a lot scarcer than the documents. Gary