[AT] Chain grades

[Bob W]

I just got some chain from a friend that did not want it (50 feet for free).
It had been given to him. My question is how can I tell what grade it is?
There are no markings on it, it is shiny almost to shiny to be galvanized.
He seemed to think it was grade 80, but I think that is what he was told. It
would be great if it was grade 70 or 80 then I could use it to tie down my
8N to the trailer (tractor reference). It is 5/16" chain. I was under the
impression the grades 70 and 80 were stamped.

Thanks
Bob W [FL]
1950 8N