Couple photo's of my mod 2000. The VCO mod on the low frequency end is .9 Mhz to 1.3 Mhz. Ismael was able to break 1 Mhz with his VCO mod to .9Mhz. This is important because the low frequencies are used to search for large gold, deep with BIG coils. Or in my case Thunting. I use my unit after I find something else and need to search deeper. The VCO mod is not a fixed frequency crystal but a adjustable frequency knob so you can fine tune your coil / detector combo.