Hey all,

I'm confused about some RCA 5751s I have. I'm still not clear, even after reviewing some documentation, what the 3 character etched codes mean...a few have a white "puffy" etched PC.

These have no code (e.g. BA, BL, or 64-52) but have etched:

PC
PC

O6N
38N
4ON
5O

Also, I'm unclear on if there is any way to distinguish COMMAND 5751 black plates from others based on construction. All have black plates, but very worn labels.

Here's the doc: RCA date codes (http://www.hifitubes.org/Ephemera/RCA%20DATE%20CODES.pdf)
thanks
J