It was a class K airless planet with no moons, blasted and bleak, barely habitable and quite miserable. However, it was the only planet in the area that was even remotely suitable for a base guarding against pirates and smugglers (likely Orions) operating across the Neutral Zone.
Thus Kelm was developed as a Klingon military base, but rumored to be a dumping ground for losers of the Klingon Great Game of politics. Not one ranking officer assigned to Kelm was ever recalled. In the late 23rd century, military governor Karab zantai-Velai was posted to Kelm following a little-known scandal.
Kelm was the headquarters of the Klingon 4th Frontier Force, which spent the majority of its time on patrol in space as far away from base as it could get.
It had a total surface area of 84,948,661 square kilometers with 100% land mass. About 45% of its makeup was normal metals and 11% was industrial crystals, while it only had trace amounts of radioactive elements, gemstones, and special minerals. It had no atmosphere and a 24-hour-long day (FASA RPG module: The Orions: Book of Common Knowledge).