This is a very unusual and highly distinctive vintage SEIKO mechanical watch, reference 21-7510, commonly known among Japanese collectors by the nickname “Momotaro.”
Momotaro is one of the most famous characters in traditional Japanese folklore. According to the story, a large peach is found floating down a river, and when the peach is opened, a boy named Momotaro appears from inside.
The nickname of this SEIKO watch comes from its remarkable case construction.
At first glance, the watch looks more like a decorative Japanese pendant or small ornamental object than a conventional timepiece. The outer case consists of two symmetrical hinged covers decorated with traditional floral motifs. When the covers are opened, the watch itself is revealed inside, almost as if something were emerging from a peach.
Because of this unique opening mechanism and appearance, Japanese collectors came to refer to this model affectionately as the “Momotaro.”
It is a wonderful example of the playful and experimental side of Japanese watch design.
The watch dates from approximately the 1970s, an era when SEIKO was producing an extraordinary variety of watches. While the company was rapidly developing quartz technology during this period, it was also creating highly imaginative mechanical watches, ladies’ watches, pendant watches and fashion-oriented timepieces.
The Momotaro is particularly interesting because the watch is only one part of the overall design. The protective outer case transforms the act of checking the time into a small mechanical performance.
Rather than simply looking at a dial, the owner opens the two decorative doors to reveal the hidden watch inside.
The octagonal geometry of the outer case, the deep reddish translucent finish, the polished metal frame and the engraved floral decorations give the piece a distinctly Japanese decorative character. A braided red cord allows it to be carried or worn as a pendant.
Inside is a small SEIKO mechanical hand-wound movement, representing the miniature mechanical watchmaking for which SEIKO was already internationally respected during this period.
The case back is marked:
SEIKO 21-7510 JAPAN
The reference 21-7510 identifies this unusual SEIKO model.
Today, watches such as this are increasingly interesting to collectors because they represent a side of SEIKO that is very different from the company’s famous divers, chronographs and Grand Seiko models.
This is not simply a conventional wristwatch.
It is simultaneously a mechanical timepiece, pendant, decorative object and piece of 1970s Japanese industrial design.
The dramatic opening case also makes it a fascinating display piece. Even people who are not watch collectors are often surprised when the decorative object is opened and a complete mechanical SEIKO watch is revealed inside.
For collectors of vintage SEIKO, unusual mechanical watches, Japanese design, pendant watches or unconventional horology, the “Momotaro” is a particularly charming and unusual piece from SEIKO’s history.
More than half a century after its creation, its unusual construction still feels inventive and playful—a small example of the creativity that made Japanese watch design of the 1970s so fascinating. The accessory for the push mechanism is missing. The item is in an open state.