I already had the coins and 5 colours of woodstain (suitable for being nibbled on / saliva proof). So I simply brushed a few coats of the stain on with a soft brush. I used an old dish towel as my working surface - I didn't fancy the wet coins sticking to paper or staining our nice table.
The stained coins were so pretty, I almost couldn't bring myself to write on them...
Anyhow, I let the coins dry for a few hours and then wrote on them with my white Posca marker. The ink kept sinking into the coins, so I gave the writing a few coats - leaving each coat to dry for a little while first. The white ink gradually built up.
There are 2 coins of each number. On the 1 side I have written the number and on the other there are dots for her to count and figure out what the number says. I should probably have done numbers 1-20, rather than 2 sets of 10...but how would I have fitted 20 dots on to the back!?