technology to make these items is relatively simple been able to do it at a cheap enough price and make it last is the problem we are seeing with deben i think thats why its not being taken on by others. having had both boxes over the years they are both similar in there use there is no black art to using the mk 3 its just the same as the mk 1 in reality. regards all the issues with the mk 3, the mk1s where also inaccurate, and often if working near a wire fence they would not read accurately and suffered from interferance, and depth was not allways accurate but they had very few breakdowns al