Recently during this discussion, I took a quick look for the instruction sleeve (that was on my visor when purchased in Apr 1976 and removed from my visor and stored sometime in the early 80's). I couldn't find it then, so I ordered a couple of the (69-72) Corvette sleeves from Corvette Central. Well, yesterday while looking for something else over in my shop, I FOUND the original sleeve from the Camaro - sticking inside an old Chilton's Camaro Repair and tune up guide!
So here is a side by side comparison of the 'Corvette Sleeve - repro' and my Camaro sleeve - original.. front and back. The differences I noted were 1) Size - the Corvette sleeve is larger for the larger corvette visor? and 2) the PN's differ by '1' (3964573 for the Corvette and 3964572 for Camaro). Both are dated 10-2-68. The textual information and diagrams are both sized exactly the same - but the Corvette is on a larger sized sleeve.
Note: The date/PN on the sleeve from my 09C Camaro is exactly the same as that posted previously by Terry69RSZ28 from his 03E Camaro, implying there was no change between those periods, and possibly no change from the date on those sleeves (2 Oct 68) until at least mid-Sept 69 and probably since that's so late, no change the rest of the production year.