My Oris ProPilot Altimeter had an error of about 10mbar on the barometer from the factory. I just finished recalibrating it, and I figured I would share the information and pics.
The back of the watch with the cover off.
The aneroid altimeter/barometer device removed exposes the Sellita SW200 movement beneath.
The flip side of the aneroid device, showing error in the barometric reading, should be ~1020hPa
I initially theorized that the barometer adjustment could be done by loosening the 3 flat head screws shown here then rotating the aneroid device relative to the outer ring scale. However the design is such that the disc is anchored to those 3 screws as shown in he red circle. The correct method of adjustment is to use the tiny screw marked by the green arrow. Loosen to increase he pressure reading, tighten to lower the pressure reading.
After calibration, checking against Elementum, and local NWS.
All closed up, everything matches up nicely.