What does “McR” marked inside a ring mean?

Here\\\’s a question that was asked about Vintage Diamonds:
I have a vintage 14KWG diamond anniversary band that has what looks like “McR” stamped or marked inside the band on the opposite side of the 14K stamp… does anyone know what this is?
Is it a designer’s initials, company mark or something to do with metal composition?
I’ve searched online and all I can find is a company that imports gems called “MCR” and billions of “My Chemical Romance” band stuff.
Any Help?