Besides metal detecting what are your other hobbies?I also work on older cars as a hobby.
Follow the Link and See if you can guess which one is me. 
http://www.chevytalk.org/forums/Forum73/HTML/000700.html
Just Curious if Detecting is your only hobby?
One more thing if you ever start to think HYPE is rampant in this hobby you should try looking at the information for automobile products. Better yet go to SEARS and ask them how an advertised & rated 5 or 6.5 HP air compressor can run on a 110 volt 20 amp breaker. 
Later,
Don(TN)