Seiko Liner Ref. 15010E – Seiko’s thin-dress masterpiece born from post-war competition This Seiko Liner Ref. 15010E represents one of the most refined expressions of Seiko’s early high-grade dress watchmaking, developed at a crucial turning point in Japan’s post-war horological history. The Liner was introduced in June 1960, during a period when the global trend in wristwatches was shifting toward larger yet thinner cases. Seiko had already proven its ability to scale case sizes successfully with the Crown, but with the Liner, the brand deliberately chose thinness as the primary technical and aesthetic statement. At that time, Daini Seikosha’s Kameido factory had already launched the ultra-thin Gold Feather. In response, Suwa Seikosha developed the Liner as a direct counterpart — not as an experiment, but as a fully realized high-grade thin dress watch. This competitive backdrop makes the Liner an essential chapter in Seiko’s internal technical evolution. Unlike the Gold Feather, which employed a completely newly designed ultra-thin movement, the Liner achieved its slim profile by refining and modernizing an existing movement architecture. The movement thickness was reduced to approximately three-quarters of the Marvel, while preserving durability and daily usability. This approach proved highly successful and contributed directly to Seiko’s later advancements in thin automatic movements. This example is equipped with a manual-winding movement featuring Diashock shock protection and 21 jewels. The movement incorporates several advanced features for its era, including Diafix jewel settings, the fully matured S-2 shock system, decorative grooves on the ratchet wheel, and triple-slotted reverse-thread screws on the crown wheel — all signs of Seiko’s increasingly sophisticated manufacturing standards. For a thin manual movement, it earned a strong reputation for both reliability and longevity. The dial design emphasizes clarity and elegance, aligning perfectly with the Liner’s thin-profile concept. Applied hour markers and a subtle sunburst finish create a calm, balanced appearance. A particularly notable feature is the script-style “Seiko Liner” logo, used only during a limited production period. This cursive signature adds a softness and refinement that later block-letter logos cannot replicate, enhancing the watch’s distinctly vintage character. The gold-plated case reflects the Liner’s high-grade positioning. With a case diameter of approximately 35.5 mm, it offers a presence comparable to the Crown, yet achieves a noticeably slimmer and more refined profile. The thin case allows the watch to slide effortlessly under a cuff, making it ideal for formal wear or understated daily use. The case thickness measures approximately 8.9 mm, clearly demonstrating the Liner’s core design philosophy of elegant thinness. The watch is fitted with a new leather strap, ensuring immediate wearability while respecting the original aesthetic of the period. The Seiko Liner was positioned as a genuine luxury model of its time, comparable in grade to the Gold Feather. Its thin-movement technology later became a foundation for Seiko’s automatic calibers, where controlling thickness would become an even greater challenge. This is not merely a vintage Seiko, but a historically significant timepiece that represents Seiko’s response to competition, its mastery of thin mechanical design, and the quiet confidence of Japanese watchmaking at the dawn of the 1960s. Running at the time of listing. As a vintage watch, stable operation, accuracy, and water resistance are not guaranteed. The watch will be carefully packed and shipped with tracking for safe delivery.