Such combo writing instruments with fountain pen and ballpoint were already available before the First World War, e.g. from Waterman; currently Diplomat or Visconti offer comparable models. The piece described comes design-wise from the 1970s and was probably made by Mutschler in Heidelberg; visually appealing, quality rather inferior. To change the ballpoint refill, this can usually be pulled out from the front, if necessary with pliers; with some models, a screw closure also had to be released from the inside, e.g. with the then popular combinations with digital watch in the upper part.