just it's big brother the Explorer 11.
All coin machines will find a nugget if it is big enough but the Explorers( Also Quattro) were not designed for very small nuggets. My Explorer 11 had little value for me as a nugget machine as it was not sensitive to small gold. In addition,the EX 11 could not detect specimen gold(wire gold, ect) which was easily detected by my single frequency detectors.(A lot of multi frequency detectors have this problem gold wire, chain, ect). So don't go in the same direction I did and expect the Exp 11 or its little brother the Quattro to fulfill the role of a decent nugget machine.
There are only 4 detectors that have the high frequency necessary for coin/relic/nugget hunting and the Quattro is not one of them. From what I have read- the MXT because of it's VDI abilities has an edge on the other three. I recommend you read Steve Herschbach's excellent article below.
http://bb.bbboy.net/alaskagoldforum-viewthread?forum=2&thread=680
George