Altimeter question??
 

On some altimeters found on light aircraft there appears to be a little white marker that moves around as you alter the pressure setting. Its often found to the right of subscale setting, on the outside. (I DONT mean the 10000ft pointer btw !!!!)

Anyone any clues????

If positioned at the 12 o'clock position, it will set Standard QNH (1013.25 hPa / 29.92"Hg).

At least that's how it was on the ones that I used.

Regards,

Old Smokey