I've owned several. All the m/t's had the marking, but some of the a/t's did too, so that's not an indicator.

I don't think it's the shifter. Sometimes the check balls that engage the detents on the shift rails are missing. The shifter is just a lever and pivot that engages forks on the shift rail, and will not affect staying in gear. I'f pull the plugs and check the detent balls and springs.

Not responsible for advice not taken...