A couple of bags
of concrete were poured into the can to provide a rock solid foundation.
The plywood circle at the top is sold at Home Depot for about $3.49. Lately I've reactivated my ATM hobby and found that since 2002 when the can was created some gaps were formed between the concrete and pier but another bag of sand / topping mix cement solved that problem!
material Copyright (C) 2002 by Gordon Tulloch ALL RIGHTS RESERVED