I have some 3/8" bolts that were manufactured by Caterpillar. They were a grade "super", I think they have 7 or 8 marks on the head. They were made in batches of 100, then 10 were randomly pulled and tested. If any failed, the batch was disposed of (which is how I got them). I figured they were still at least grade 8. They have an oval with the marks all on one side.
http://www.engineershandbook.com/Tables/boltgrades.htm
Bob
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