How much is a Seiko Seikomatic Weekdater 6218-8971 worth?

Where the data comes from. From Catawiki's watch auctions — an automatic census notes every lot closing each day and, at close, records the final price and whether there was a buyer; a lot that closed without a buyer is a sale that didn't happen, because the bid didn't reach the seller's reserve.

The auction houses. Since September 2026 the public hammer prices of Fellows and Watches of Knightsbridge (Birmingham and London) and of the Nordic and German houses on Auctionet are included too. Each charges the buyer a different premium (Fellows 30%, Knightsbridge 26.4%, Auctionet around 25%, Catawiki 9%), and since people bid knowing what they will pay in the end, every hammer price is converted to its Catawiki equivalent for a like-for-like comparison: hammer × (1 + premium) ÷ 1.09, in euros at the European Central Bank rate of the sale day. Each sale shows the original hammer price and the house.

Which price it is. The hammer price: what the buyer bid, without Catawiki's buyer's premium or shipping. To compare with a shop or a listing, add roughly 9%.

How it is calculated. The usual price is the central value of the sales: half closed for more and half for less. It is deliberately not the arithmetic mean: a single odd sale — a gold model among steel ones — would skew the mean, and this calculation is unaffected.

What it is not. An appraisal. Two watches with the same reference can be worth twice as much as each other depending on condition, whether they keep box and papers, and whether they are original. Look at the sales one by one before deciding.