In the golden age of Martinis (1950s and 1960s), a number of fantastic gadgets were invented to help preparing Martinis, typically aiming to make sure Martinis were as dry as possible (at that time the quest for the driest possible drink had started already). Some of these gadgets exist still today, such as the Vermouth atomizers, others are no more produced and are very difficult to be found.
In 2020, the Summer Cup blog has collected a number of these gadgets, analysing them with a lot of irony and acually testing them in real life. Have a look to check out their experiments: https://summerfruitcup.wordpress.com/tag/martini-gadgets/.
Here come one of the funniest one: the Martini Stones.

Martini stones were produced by Podam Co. Illinois in 1963. They are actually real stones, that you should imbibe in dry vermouth, keep refrigerated, and then put in your martini glass to give that minimal vermouth flavour to your drink, creating a “very dry” Martini. Probably they derive from the technique of soaking olives in vermouth before adding them to the drink: since the olives transfer too much vermouth to the gin, the “Martini Stones” were invented. See here below the original instructions of the gadget:
The Summer Cup blog experiment concludes that the Stones are sort of useless, since the result is is practically a glass of chilled gin. From an aesthetic point of view, the post states that “the stones look pretty in the glass, but are not very effective for making a Martini; maybe this is why they’re not made anymore…?”
If you want to try out this gadget, today you can go for for Whisky Stones. I bough these, and I have to tell that – similarly to the stones of the 60s – these don’t really add anything to your drink. Still, the idea of a Flinstones Martini is not bad…