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You have made a truly amazing ring. One bit of advice if you make another is to dilute the Ferric chloride down so that it works slower, this lets you control the amount of etching that occurs.
The egg timer is a silicon/plastic ball the size of an egg which slowly changes colour as it heats up. You place it in the pot with the eggs and when the colour change reaches the desired mark on the red card inside you know how cooked the eggs are.