[Boatanchors] OT? What kind of units are Mandrels?

[Ian Wilson]

I have a Simpson meter, appears new. The box used to say Model 55,
0-25 AC Amperes.

The meter scale itself says MANDRELS, is a 0-25 scale with the 0-5
being compressed and the 5-25 being more or less linear.

The scale looks professionally made. It also carries the legend
74-RA-42 under the "MANDRELS" word.

I have not been able to find a meaning for "mandrel" other than as a
sort of former, nothing to do with units of measurement certainly.

Any leads O Anchored Ones?

73, ian K3IMW