Plastic military dog tags are the most durable material and they are extremely hard. Check out the manufacturer's mention of dog tag on Alibaba.com.
The most common materials for blank engraving dog tags include 50 polyester, which is very durable and is less washable than plastic dog tags. Plastic dog tags are an essential material of a dog's life. Buy bulk military dog tags made of plastic, nylon, and other durable plastic dog tags.