For "mark" as a sign or indication:
* Landmark: A significant or prominent feature.
* Watermark: A mark or design embedded in paper.
* Bookmark: A marker used to indicate a place in a book.
For "mark" as a grade or score:
* Grade mark: A mark given for schoolwork.
* Test mark: A mark given for a test.
For "mark" as a physical trace:
* Footmark: A mark left by a foot.
* Handmark: A mark left by a hand.
* Fingerprint: A unique mark left by the ridges on a finger.
Other possibilities:
* High mark: The highest point reached.
* Low mark: The lowest point reached.
* Trade mark: A legal mark identifying a brand.
* Target mark: A mark aimed at.
Ultimately, the best compound word will depend on the specific meaning and context of "mark" in your situation.