O.B. McCLINTOCK 3-Scale Milliamp Meter Shunting

[W9ZSL]

So I bought this meter awhile back and now I'm wondering what to do with it.  It is identical in appearance to a Simpson model 27 including the art-decco housing.  The scale says "Made by O.B. McClintock Co Minneapolis, Minn, U.S.A."

The scale is 15, 150 and 300 MA.  I measured the resistance at 6.7 Ohms.  I assume that "as is" it is good for 15 MA and I'll have to provide shunts for 150 and 300 MA?  I'm thinking of using it with a single 813 to measure plate, screen and grid currents.  I'll be running close to 1500 VDC on the plate and bias/screen voltages accordingly.  Any thoughts?

[Opcom]

Meters like that sometimes have no relation between the scales and the full scale current. Best to test starting low.

[W9ZSL]

That's what I thought too.  I have a 15 MA meter and shunted it to double the current to 30 because I needed to see 27 MA on an oscillator/buffer.