if you have the SL eng trinket learned, all your alts and attached accounts can use the toy once they learn SL eng,
i use it to get a few FPs in each zone then unlearn eng. unless i want to keep the port option.
i try to check the house of plagues pool when players summon the rare that drops for a 20 the ilvl54 blue trinket with 7 stat and 11 leech. it can upgrade but that is rare