What is this chain labeled M3

[Paul Van Benschoten]

I have a bucket of 5/16 inch chain with M3 stamped every few links. I think it is about 75ft long. It also has USA stamped on some links.

I searched chain grading sites, but I could not find anything with M3. Maybe this is just another form of 30 grade?

I've had this chain for years and never used it. I figure it is time to sell it and someone will ask what the M3 represents.

Does anyone have a guess?

 

[Eugene]

https://www.1st-chainsupply.com/aboutgrading.htm

GR 30, proof coil. - - - - Manufacturer's mark, grade 3.

 

[Paul Van Benschoten]

GR 30, proof coil. - - - - Manufacturer's mark, grade 3.

Thanks Eugene. I had seen that site but I didn't realize the M was just a manufacture's mark.