I am going to chime in here on this as it could very well be a problem from the factory. This exacts issue happened with the first Gold Bug Pro's..we could not detect big silver...dimes were o.k. as were quarters but silver dollars...invisible...and the cause was this. When they set the internal Ground Balance offset they use a piece of Ferrite to calibrate this. By mistake they techs had set this point wrong....it was mistake. This calibration is crucial to be exact because....it affects the machines VDI scale when properly ground balanced...and if it is wrong then the VDI is off also. What this effectively does is push the VDI of targets up the scale and where big silver used to VDI at say 88...it pushed it up and out of the upper ID range and into the ground balance range effectively causing you to GB out the ground..and big silver and BIG silver would not ID it at all. Most of use had to send em back in and have them recalibrated. When they came back they worked fine.Fisher ID machines do not have enough top end discrimination adjustment on most of the F machines to allow you to disc out yourself any silver....so it is not a disc setting. You need t call the factory......now they did tell us an easy way to check our gold bugs by using a piece of ferrite to see what the ferrite id at or maybe we used it to do a GB....I forget but....the ferrite should have read a particular number within 1 digit and if it did not then our cal was off....and it was.Actually...I think what we did to check was get a piece of ferrite from radio shack...then use the ferrite and ground balance the detector to the ferrite until the detector was balanced to the ferrite...no change in threshold....then read the GB value. This told the techs if the calibration was off. So.....do not panic....but you cannot set the machine so it can't hit big silver at 2"......you most likely have an internal GB ferrite calibration that is off.scott