These are called planchettes and are a security feature. They are incredibly thin discs that are mixed in with the paper randomly. If they are near the surface, they can be picked off. Some fluoresce under UV light and others don't. They've been used in many paper banknotes for over a century. The ones in banknotes are usually green, but there are yellow ones in Canadian Tire Money.
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BWJM, F.O.N.A.
Life Member of CPMS, RCNA, ONA, ANA, IBNS, WCS.
President, IBNS Ontario Chapter.
Treasurer, Waterloo Coin Society.
Show Chair, Cambridge Coin Show.
Fellow of the Ontario Numismatic Association.
