Memory lane time.
Alas, I also cannot find any web sourced Post Office type instructions for the Tension Gauges, although we had an Australian PMG Telephony Equipment book for instruction in the 1960s.
Essentially though, the items were a type of spring tension gauge, with thin detachable end sections, which were inserted into the gauge end mechanism, and as desrcibed in earlier posts.
The required "tension" to be tested, in grams, was adjusted with the knurled knob.
The whole gauge was held in one hand, and in a horizontal position, and the end of thin extension was placed under (or over, as required) the extreme end of the relay contact spring.
The gauge worked in one "direction" only. If used "over" a contact, then the gauge was rotated in the hand so the scale is away from the operator.
If the relay contact spring was adjusted correctly, then with slight vertical motion of the whole gauge, the gauge spring mechanism would let go with a definite "click".
Otherwise the actual tension could be measured by turning the knurled knob up or down to determine the click point, thus indicating the tension.
These gauges were used to check the tension of a relay contact against a stationary insulated block, or to check the tension of a moving contact against a fixed contact, when the relay was operated.
The tension was in grams, probably because BPO 3000 relays and earlier types appear to be an Ericsson design.
The gauges were also used for other higher value tension measurements in electromagnetic items eg Strowger units and Uniselectors.
You can see some of the test procedure on page 7 in this document
http://doc.telephonecollectors.info/...type_ocr_r.pdf
Unfortunately only a small section of the end of the gauge extension is shown.
These gauges were included in a larger collection kit of special tools for Telephone Exchange equipment.
And as the 3000 type relays (and 600 type and others) were widely used in equipment rooms and in radio and electronic equipments, the relay adjustment kits were relatively common in the 1960s.
Each kit that I saw and used (only occasionally) had three or four tension gauges, to measure approx 25 to 500 grams.
The kits had other relay tools, and the photo shows what's left of my collection, just a few, with "other" uses.
I have a relay contact stroking tool here somewhere.
Its use, as depicted in the B5144 booklet, is a precision hand skill, but easier after you have done it a hundred times.
You can calibrate these gauges using a small plastic freezer bag (ie about 1 gram) with say 100mL of tap water. Trip point will be 100 gram.
These Gram Gauges are useful, and I would keep them.
They are relatively common though, so sale may not reward a seller as much as first anticipated.
Good luck
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