A method of manufacturing a pen drug delivery device comprising the steps of (i) providing a drug delivery device comprising a dose indicator member adapted to move relative to a housing during dose setting and dose expelling corresponding to an axis of rotation, the indicator member having an initial position corresponding to no dose amount being set, (ii) arranging the indicator member in the initial rotational position, and (iii) providing on the housing and on the indicator member respectively a pair of zero markers having a predetermined rotational offset. By this arrangement the issue of finding the correct initial (zero) rotational position of the indicator member is addressed by providing corresponding and rotationally paired zero markings on the pen housing and the indicator member after the pen device has been assembled, this allowing the “true” initial position to be detected by image capture and subsequent image analysis.
