In addition, there are quite a few Mark V's that come up for sale on e-bay regularly.  The price for Mark V's seems to between $50 and $100.  In the last two weeks I have seen 4-5 Mark VI's.  The price I have seen for Mark VI's ranges from $125 to $250, which seems about right to me for something that (to quote a seller who was shocked she got $125.00 for her Mark VI) "wouldn't bring 25 cents at a yard sale."  :o-)   It is really remarkable that such a simple machine brings the prices it does.  I wonder how much galvanometers would sell for in a truly free economy.

Niteroi