This is a lapel buttonhole device, and not what I would technically refer to as a ribbon bar, in the normal sense of a full size ribbon bar that was worn on a military tunic or coat. Your item was worn on the lapel of a civilian coat, in the buttonhole of the lapel. You'll notice the metal button on the back side of the device.
Yes, this is the Honour Cross of the World War, or in the German language "Das Ehrenkreuz des Weltkrieges 1914/1918". Some people commonly refer to it as the Hindenburg Cross with Swords, which is the version for combatants.
Congratulations on receiving this nice gift from your father.
The medals are confusing at first for beginning collectors, because there are so very many of them awarded by not only the Imperial German Empire, but also by individual German states. Acquiring a copy of the book "Deutsche Orden und Ehrenzeichen 1800-1945" by Jorg Nimmergut is a good reference book to learn from, and it also gives prices which are recognized by collectors and dealers. The newer editions of the book have nice color photos, and many more photos than the original issue books did back in the late 1970's or early 1980's when they were first published, which simply had a few scattered black and white photos in the older editions. A new volume comes out approximately every 4-years with updated prices.
Here's a link to the book:
https://www.amazon.com/Deutsche-Orden-und-Ehrenzeichen/dp/3866461429
Best Wishes,
Alan