[Test-Equipment] TM4520 inductors

[Stewart Bryant]

Does anyone know the original purpose and
rated frequency range for the Marconi TM4520
inductor set?

The individual coils are marked TM1438/letter

I have been using then to compare a number
of inductance meters with inconsistent results
and wondered about the construction, frequency range
and as they are in a nice polished box, whet their
provenance was. (I picked them up for pence at
a flea years ago because no one wanted them).

I note that they were used to calibrate the
AADE inductance meter

http://www.aade.com/lcm2binst/HP.html

and that they are a museum piece,

http://www.porthcurno.org.uk/html/arc_result.asp?SearchText=1438&sType=any&recNo=0

but I wondered if anyone knew any more.

Stewart/G3YSX