Automatic K-402
1956–1957 · 10K yellow GF · Automatic
About the Automatic K-402
Made from 1955 through 1957, the Automatic K-402 runs on Hamilton's caliber 661, a 17-jewel automatic that was part of Hamilton's push into sweep-seconds dress watches during the mid-1950s. The case is 10K yellow gold-filled, circular, and 12mm thick with 17mm lugs, giving it a presence on the wrist without being oversized. Hamilton offered it with two distinct dial options: a black dial with yellow embossed numerals and luminous dots, or a white dial with embossed gold numerals, markers, luminous dots, and a pearled track. The K-402 is part of Hamilton's broader Automatic family, which spans a wide range of styles and price points from this era.
Embossed numerals hold up better than printed ones over time, so dials on the K-402 tend to age with more dignity than some of its contemporaries. That said, the luminous material on older examples can discolor or flake, and original lume plots should be examined closely. The two-dial configuration means you occasionally find both variants in circulation, and the black dial version in particular has a crispness that holds up well against the gold-filled case.
From the Catalog
Hamilton marketed the K-402 in 1955 as shock resistant, anti-magnetic, and waterproof, positioning it as a practical dress watch for daily wear. With a bracelet, the black dial version retailed at $95.00, while the strap configuration came in at $89.50. Note that vintage watches originally rated waterproof should not be trusted for water exposure today without fresh seals.
Hamilton Catalog Images
1955
1957
What to Look For
| Dial | Check the embossed numerals and markers carefully. They should be crisp and evenly raised. Look for any flaking or discoloration around the luminous dots, and on black dial examples, watch for uneven fading or spotting near the center of the dial. |
| Crystal | These take an acrylic crystal. Light scratches can be polished out, but deep gouges or crazing mean it needs replacement. A clear, undistorted crystal makes a real difference on a watch with this much dial detail. |
| Movement | Dried lubricants are the most common issue with unworn or stored examples. If the sweep seconds hand stutters or the watch stops after a few hours, assume it needs a full service. The caliber 661 is a solid movement, but it does not tolerate old oil well. |
| Case | On this model, the case opens through the crystal side rather than the case back. Pry marks or scratches around the case back are a sign someone tried to open it the wrong way. Check the gold-filled surfaces for wear-through, particularly on the lugs and case back. |
| Crown | The crown should seat firmly and wind smoothly without slipping. A worn or replaced crown can affect the watch's overall look and function, so confirm it's the correct profile and pulls out cleanly into hand-set position. |
The Movement
The caliber 661 is a 17-jewel automatic movement that Hamilton used across several of its mid-1950s dress automatics. It winds via a rotor with no manual-wind option, so it relies on wrist motion to keep the mainspring charged. It's a competent, reliable caliber when properly serviced, though the oscillating weight assembly requires careful handling during reassembly.