The Non-Marring Brass Metal Detecting Probe. When metal detecting for coins or other valuables, you need a tool that won’t damage any potential finds. Brass won’t ruin the artefact, coin, or metal you are searching for as you use it to probe deep into the earth. The 6.25″ rod length lets you get deep into the earth or sand to find out where the coin or other treasure is hiding without taking up too much room in your utility belt or waist pouch.?