The Seiko 6R35 automatic caliber

The Seiko 6R35 caliber is an automatic movement in Seiko's high-performance 6R series. The caliber is an improved successor to Seiko's famous 6R15. Aside from its slightly lower height, the 6R35 caliber maintains a power reserve of at least 70 hours, 20 hours more than the 6R15. To fully wind the mainspring, the crown must be wound a good 50 times. Similar to the famous 6R15, the 6R35 caliber is now used in many well-known and popular Seiko models, such as the Seiko Prospex, Seiko Alpinist, and Seiko Presage "Sharpe Series."

The 6R15 caliber is used in many Prospex Sumo Diver models , such as the SPB183J1 Captain Willard (Apocalypse Now) ltd. edition or the SPB097J1 Twillight Blue .

6R15 vs. 6R35 – the direct comparison

the two calibers are practically identical:

The only, or rather significant, difference is a 20-hour longer power reserve for the 6R35 caliber. Regarding accuracy, Seiko notes that the specifications apply to a normal temperature range between 5 and 35 degrees C and when worn on the wrist.

The Seiko 6R15 caliber – a success story

Seiko's 6R15 caliber was introduced in 2005 and quickly became one of the most widely used and best automatic calibers. By using a different spring, the Spron 510, the power reserve and accuracy were increased compared to previous models. The 6R15 caliber was also inexpensive, which contributed to its success. The caliber was and is used in many Sumo and Alpinist models , for example.

These Seiko models in our shop are equipped with a 6R15 caliber: https://myfinejewellery.at/search?type=product&q=6r15

Although Seiko continued to introduce new calibers, the 6R15 remained a popular bestseller and continued to be used in many models. The great advantage of this caliber is that it operates almost like a so-called high-beat (fast-oscillating) caliber, but retains energy longer—and is much cheaper than a fast-oscillating caliber.

The Seiko 6R35 caliber – an upgrade

Can something almost perfect be improved? In 2009, a modification of this successful caliber was introduced, the 6R35, which now beats in most Prospex and Presage models . Here's a selection in our shop: https://myfinejewellery.at/search?type=product&q=6r35

As already mentioned above and shown in the comparison – according to the motto “never change a winning team”, the upgrade in the form of the 6R35 caliber differs primarily in its impressive power reserve of up to 70 hours, which is a full 20 hours more than the 6R15.

The newer 6R35 caliber also offers extremely high quality automatic movements in the mid-price segment (from €7 to €800) up to the higher-priced Seikos. From the current 2022 "Black Series" collection, the SPB253J1 model is an example: https://myfinejewellery.at/collections/herrenuhren-aktuell/products/limitiert-seiko-prospex-black-series-spb253j1-herrenuhr