The most common grade marking system seen on Imperial size hex bolt heads is the US ASTM/SAE scheme, which is an ANSI Standard. Metric bolts use the ISO 'x.y' numerical grade markings.
These markings don't resemble any in these schemes, so I'd say Grade 2 at best.
Cheers,
Gadge
"ODK Mods can explain it to you, but they can't understand it for you..."
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