Interesting. I should write some code for mine and check for that bug. I assume it was fixed by the time this shipped (my CPU is week 21 of 1976). I have an acrylic case for mine to protect it.
You might indeed have one with a bad ROR. My MOS documentation for the time says ROR would be "available" after "June, 1976." The Rev A here is 30th week 1976 and does not have the bug.
