This priceless artifact is guaranteed to find only unexplored potholes.

Results proven by many (unverifiable, undocumented and unrepeatable) experiments.

A snip at £20,000. (cash only, no receipts)

see http://www.ukcaving.com/board/viewtopic.php?t=1863&start=0

for further info.

This wouldn't be the "emotionally attached marble" lost in Swildon's Hole and mentioned by Cap'n Chris in the "Lost and Found," would it?