Modified White's Classic II SL Air Test

Checkout the depths a modified White's Classic II can potentially achieve. He added a ground balance and threshold to the detector. White's Classic II's can be bought for a really cheap price so if you have some knowledge on how to modify metal detectors, or know someone who could do it for you it makes sense to buy one. I mean, 13 inches on a Twenty pence coin! 15 Inches deep on a 2p coin, and 17 Inches on a 2 Pound coin. And not forgetting a Foot deep on a Gold Ring! Wow! Can the detectors costing upwards of £700 detect similar items that deep? Very impressive depths for such an old detector.