expanation of this disc welded to frame?

I know that this topic has probably been discussed before but I at some point missed it. I was doing a mild resto on a friends 71 charger and found this disc with numbers partially welded to the front of the K frame. Would someone explain to me what it was for? Thanks.

Last two digits of the factory part number for assembly line ID purposes of the original part to its application.

If there is a broadcast sheet for the '71. what does it say in the 'FRAME' section on line 4?

that sheet has been long gone. This is a really rough shape car. It belongs to a friend who passed away 2 years ago and his wife won't let the car go and had me freshened up the drivetrain and rewire the car as her husband messed up the wiring over the years he had it. She wants to keep it in the family and have her son take her riding in it on occasions. I happened to notice this disc welded to the frame and was curious of what it was for. Thanks.

the only K-frame "90" or "06" I see listed in GG's "white book" is:

2962090 = 1970 B-body w/318 & 383 - it will physically bolt in but the steering box mount is at a slightly different angle compared to a '71 B-body part.

can you read the date on the front center of the K-frame?

Thanks for the info. I did pressure wash the K member but didn't pay attention to numbers but will look and see what I can find. I appreciate it.

Is that actually stamped? Or is it just painted?

Mine is stamped "90"

I've heard of these referred to as "The coin".