Welcome to the forum, Spacemonkey333. In fact, you have a Late Wartime 2nd Variation Police HSc manufactured in April 1944. The finish has deteriorated significantly, probably from being stored in the leather Holster and not being cleaned and oiled for quite some time. The Holster is a German Army style and not Police.
Because of its deterioration, your HSc has lost considerable value and is of little collector value, perhaps $300 to $400. But you have a fine memorabilia of your Grandfather. Hope that helps ... anything else, let me know.