[mornflt]

I have made the same mistake.  Now what I do is to use a mild dish soap well diluted in water.  The trick is to find the small lettering and or number which identifies the dial, write the number down for further reference and then lightly wipe over this part of the dial. If this does not remove the lettering, it is generally safe to use this method to clean the rest of the dial.  I also understand that mineral spirits can be used as well.