Link says minimum level is 10 but that sounds a little high to me. Any level 15+ who is standing around erudin can (and probably will) help you kill this shark if you intend to try the quest.
http://wiki.project1999.com/Barnacle_Breastplate_Quest
Unfortunately most of the popular low level quests are for exp, not items. We are now 5+ years into blue server and its much much easier to buy low level items than to quest them. You can get quite a few solid low level weapons on p99 for 100pp or less, and often higher level players will straight up hand you a free weapon or some armor if you just started