I made my own out of aluminum tags and cut up old metal hangers. I cut the hook off metal hangers and threw it away. Then I cut the rest of the hanger into 3 pieces. I bent a loop at the end of each piece and used it to hang the aluminum tags. The tags can be engraved, so it will never wear off. The only problem I have had with them, is accidently pulling them out while raking up leaves in fall and spring.
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x---cut here
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cut here--- x x---cut here
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^ cut here ^ cut here
Hope you can understand the picture. After I cut the hanger with tin snips, I used pliers to make a curly loop at one end of the metal hanger piece to hang the aluminum tag.
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Below is a pic of the tags. I think you can get them from some sights for around $10.00 for 100 tags.