Hi Tim,
there is a spray that deters 'little knowledge eaters' ....I believe it is safe on paper etc. .....might be worth a try.
Hi Fearn,
all the Chinese coins I can find pictures of have a singular hole...usually square. Also pictured below is a coin sword 18thC-19thC British museum.....again notice the singular hole
"....Coin-swords were a form of talisman used in southern China to ward off evil influences, especially those causing fever. They were made by tying together 'cash' (the pidgin term for Chinese coins with a square hole in the middle) on to an iron rod......"
Regards David