Medicinal rum in a bottle is found by Roger in one of the stores cupboards behind the bunks on Goblin. He asks “What’s medicinal purposes?” as the bottle has a label on it. But Susan says “Put that bottle away. That’s rum for Jim’s uncle. Jim says his aunt always writes 'Medicinal purposes only' on the label. It’s in case one of them tumbles overboard or gets a chill or something, not for general swilling" (WD7). But the reference to the aunt who "always" writes a label suggests that medicinal doses are not uncommon.
When Daddy comes aboard, the pilot has said he will not charge for his services, so Daddy says "Have a drink anyway" and then asks "Was there a drink on board?". Titty says "There’s the medicinal rum .... " and Susan brings up the bottle and two mugs. Daddy pours out the doses (WD21).