Thank you, 73DAD! Finally some REAL information. Ignorant blanket statements like "all Grade 8 bolts are made in China" really p!$$ me off. It's like a knee-jerk reaction. It's automatic with no thought or knowledge to back it up. It also is a disservice to those American companies and workers who are making good products in the USA. How do you suppose they feel when they run across such an ignorant statement? All their hard work is for nothing?
The marks on a bolt head are not cast. They are formed when the bolt head is forged. Part of the marks are specific to the company that makes them.

Do a Google search for Bolt Head Markings and see many many pages of information.

R.