So I needed some high tensile bolts that are around Grade 5-8. I scratched around in the shed and came across these ones from years past. I can't recall purchasing them but I guess they came from a local hardware or chain store.

At first I thought they must be Grade 7, but now I wonder if this is just a brand letter "L". It looks more like an "L" than a "7". As for the other three markings on the head, I have no idea. Perhaps this is meant to represent three lines, but it actually looks more like a brand to me. The bolts are zinc-plated not stainless.

I just want to be sure they are the right grade for the job. I know the old saying is, "If you can't read a grade marking, always assume a bolt is Grade 2 or less to be safe."

But I thought I'd post up a pic in case someone is familiar with this brand of bolt and can shed some light on the strange head markings? [Linked Image]