Also have a 2010 build date (s/n 6101463), calibrated by Lupe, great depth, excellent performer. Had a second calibration done in 2011 by ER after a coil replacement (wore through the first coil, goes without saying I use a coil cover now). Still performs as good as before. I usually run my sensitivity at or near max as conditions allow. I must say their service and turn-around time is excellent!