Rock River. And Square mark in mold

[Farmritch]

I read where this mark has significance as to who made the receiver.
Or some type of quality mark
its also on the carry handle I have
can someone tell me the story?

thanks
Farm

 

[Tombs]

The American Brass and Aluminum forge.

Brass Aluminum Forging Enterprises | Leading Producer of Brass, Copper, and Aluminum Forgings

It's just telling you where that specific part came from.

My FN and Colt both have the square. And even the carry handle on the Colt has the square.

My old RRA has the keyhole, and my PSA has the A.

 

[BiscuitsandGravy]

https://www.indianagunowners.com/forums/long-guns/328500-need-info-who-made-ar-upper.html

 

[Farmritch]

Who can identify this mark??

 

[BGDave]

Cardinal Forge.