In E-mail's, Dave offered me these results in some
comparative testing he did.

First E-mail from Dave on April 2 2004:

Amazing! After playing around with VR1 and settling on 0.3 volts for VR1,
I took measurements for a 1 oz Silver Coil, a Pop Can and an 8 ounce copper pot.
The Commerical Detector is a JW Fisher, Pulse 8X

Detector      Coin  Can  Pot

Gary's         8"   15"  23"
Commerical     8"   14"  23"

I gradually moved items closer and listened for an easily noticable change in the
audio beep rate (didn't use the meters)
A 7.5 inch Commerical Coil was used on both machines.
(It came with this $1700.00 Detector.)

Second Letter from Dave on April 3 2004:

Here's More Test Data, this time with a 16 inch coil instead of the 7 1/2 inch one.
Yours did *Much Better* this time with the bigger coil size than being a commerical
box. My meter says the 16 inch coil has 205 uH; the 7.5 inch coil = 230 uH

Detector      Coin  Can  Pot

Gary's         11"   23"  33"
Commerical     9"    18"  27"

NOTE:
This Info is Re-Written here, Exactially As it was given to me in the E-mails.
I am just passing it along for those who may have interest in it.
Dave didn't say who or what this 16 inch was, other than a Commerical Made Coil.

Additionally I have no Idea how this would compare to my home-made Coils or yours.
I definately find this interesting and Encourging, But I make no claims on the
accuracy or Valadity of these tests.