Thanks Axstar & Fermata for the info as well as Rickdog & Cdef for schematic and diagram respectively.
Decade switch term comes from the solder-sniffers' decade box:
Decade box - Wikipedia
"Decade" — I think because you get 10 different values to each knob (though there are other rotary switches that have more/less discrete settings).
You can buy them, but I think it's more interesting to make one myself to better meet my own needs.
Build a Resistor/Capacitor Selection Box
Make a Variable Resistor With 1 Million Settings
Project: DIY Resistor Substitution Decade Box | KJ6CQC Missoula, MT
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Then again, not sure what my needs are just yet...
Might just get Link Removed:
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or a kit:
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I'm sure there's other kits or DIY ideas out there.
Do these things work a lot like a Stellar Tonestyler?
PS "You can buy them, but I think it's more interesting to make one myself to better meet my own needs." is a good point, but it's faster to buy one