TSGL: Deep-Probe Studfinder?

[Geoff Glave]

I've got an old house, with some old-school drywall (not lath-and-plaster).  The studs are covered in a layer of drywall, then a layer of "cementy-plaster", then a layer of plaster.  You can see a picture with the three layers here:

http://members.shaw.ca/glave/wall/wall7.jpg

I'm trying to find a good studfinder that can 'see' through all that junk.  So far, the two I have don't do a very good job, and I haven't been too successful with the 'rap a knuckle' technique.

Does anyone know of a good studfinder that will see deeply through some wall-weirdness?

Thanks in advance.

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