I make the original Brain Tuner BT-5 unit. I worked with Dr. Bob Beck and assembled many hundreds or thousands of these units myself. I only made one modification to protect the IC chips in case the polarity is reversed and Dr. Beck approved this modification. I have 3 on stock as of 4/42013 and will make more of them when I get some printed circuit boards made.
My email is vertualfrank@yahoo.com
I used to make the PC boards for this device myself drilling the holes by hand etc. The BT-5 unit comes with original articles that came with the unit from Omni Magazine etc. and also the manual and there is one set of electrode headset and these are $30 for extra sets.
I make no claims only that the units that I make are from the same design and Printed Circuit board that Dr. Robert C. Beck designed himself and I use the same parts. I sell the BT-5 units for $170 which is a good deal considering that they were sold for double this price, much more than that in late 1980s and early 1990s considering inflation.