The 1980s Santos, with eight sides and a black dial.

Alberto Santos-Dumont flew over Paris in 1906 and complained to his friend Louis Cartier that he could not check a pocket watch with his hands on the controls. Cartier made him a watch to wear on the wrist with a square case and exposed screws, and put it on sale in 1911. Every Santos since has kept the screws.

The Octagon is the 1980s reading of that design: the bezel cut to eight sides, the screws kept, the bracelet made of screwed links that flow into the case. Cartier made it in steel, two-tone and gold, in quartz and automatic, and in sizes that today read as women’s or unisex.

The seller’s description says the watch has an automatic quartz movement, which is two different things; the Santos Octagon was made in both, and the photographs do not settle it. Ask the seller before buying if it matters to you. The condition is Excellent with faint tarnishing to the hardware, and the bracelet is the original screwed-link steel.

Every figure here comes from the listing and from Cartier’s own history of the Santos, not from handling the watch.

Cartier is pre-owned only on Amazon. This unit is sold by What Goes Around Comes Around through Amazon Luxury Stores, authenticated by the seller with Amazon’s return window on top; it is one piece, and when it sells the listing goes away, so the second button opens the live search for Santos.

Vintage steel Cartier has held its audience and its resale better than most quartz watches of its era; that is a pattern, not a promise, and nothing here is investment advice.