Pocket watch with alarm - Iron - 1910-1920

Very rare rectangular rock-fortress pocket watch with alarm; late 19th / early 20th century. It runs and is functional, including the alarm function. The alarm is set via the rotating glass; the watch has, next to the crown, a tiny button that must be pressed, after which the time can be set via the crown. To open the case, there is a tiny button on the underside that must also be pressed, allowing the back to be opened. On the rear lid of the case the following is inscribed: Patent No. 17104 and D.R.G.M. - No. 97674