Explorer Jack's helmet (disguised) was removed from RuneScape after an update, but still exists in-game for those who had obtained it.
Explorer Jack's helmet was a reward from the Lumbridge Rebuildathon. It could be obtained for free by talking to Foreman George and selecting the rewards option. The helmet has a disguise option that removes the monocle and mustache from the headwear, becoming the undisguised Explorer Jack's helmet. The hat can be reclaimed from Diango.