They will need more evidence than just your word. I took some time to find other sources of what you're saying. The best I came up with is a foreign site containing a guide on how to make money killing HHK Guards dated 2002.
http://www.mmorpg.pl/viewtopic.php?f=16&t=4051
I threw it in a translator:
Here is the mention of gems:
Loot:
Captain Boshinko throws 0-7 pp, a sword worth 1 pp and from time to time gem (40-60 pp)
Ordinary guardzi 0-6 pp and fs short-swords.
Here are the spawn times mentioned including 6min for captain:
Spawn time to 20 minutes Except Blayle are on the ground floor, Chopin on 1 floor and one guard in bedroomie at the same level (3 minute spawn)
The captain on the ground floor is 6 min respawn.