[werk_ag]

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The marking on the capacitors is 104 which I understand to mean .1uf or 100nf or 100000pf (I think that's the correct number of zeros!). However, when I measure the capacitor with my meter I read about 46nf or about half the value I expect.

Is this normal/OK?

You are right, 104 is the correct mark for a 100nF capacitor.
I believe that common capacity meters aren't able to give precise capacity readings, at least that is what happens with my capacity meter.