Inasmuch as I primarily detect private property with a contract, I have the option of taking coins home to soak in bottled water until I can read a date. Sometimes I clean the particularly dirty coins with bottled water and baking soda in the field to find dates & mint marks. When there are just a few coins in a yard, I gently clean them there, but as with the current property I'm detecting, I'm already up to 170 coins, so I'm cleaning them at home just to read dates and mint marks, for a complete settlement with the property owner when I've finished the property.
Respectfully,
The Nutty Teacher