Drawing Notations (Abbreviations)

[ukesoccer]

I'm really having trouble locating standard notations for engineering drawings.

The biggest problem I'm having right now is understanding crosshair notations for holes. I'm trying to interpret a 20 year old Mylar from Canadair (Bombardier Aerospace)

Its hole locations for a 0.190" Al 2024 part, identified by a + with numerous notations on each corner

Here are some examples

BB|4N
-----
CC|

BJ|5
-----
|

BA|5F
-----
C|

AO|4F
-----
|4

For example the number in the top right would be the dia. in 32nds, I think, C stands for countersink in the bottom left. But I really dont understand the top left? Or unless Im reading this completely wrong
Any idea????

 

[borgunit]

Would they be just unique identifiers?

"Everybody is ignorant, only on different subjects." — Will Rogers