Automatic K-351
1955–1958 · 10k Solid Yellow Gold / Stainless Steel · Automatic
About the Automatic K-351
The Automatic K-351 was produced from 1955 through 1958, placing it firmly in the early years of Hamilton's American automatic lineup. It runs on the caliber 661, a 17-jewel automatic movement, housed in a 10K yellow gold case with a stainless steel back. The dial is two-toned with embossed gold numerals and markers at 3, 6, 9, and 12, a pearled track, and luminous dots outside the hour markers, all read by a sweep seconds hand. It is part of Hamilton's broader Automatic family, which expanded rapidly through the 1950s as automatic movements became the expected standard for daily dress watches.
The two-toned quadrant finish on the dial is the detail that tends to catch people first, and it's also where condition problems show up most clearly. Look closely at the dial surface before anything else, because the finish on these is not forgiving of moisture or mishandling over the decades. Finding one with the luminous material intact on both the dots and the hands, without heavy tropical spotting or flaking on the quadrant sections, puts it in genuinely good company.
From the Catalog
Hamilton listed the K-351 at $125.00 in 1955, marketing it as a 10K yellow gold, stainless steel back automatic with sweep seconds, embossed luminous-dotted dial, and claims of being anti-magnetic, shock resistant, and waterproof. That price point placed it comfortably in the mid-range of Hamilton's automatic lineup for the period.
Hamilton Catalog Images
1955
1957
1958
What to Look For
| Dial | The two-toned quadrant finish is the most vulnerable part of this watch. Look for fading, spotting, or discoloration between the quadrant sections, and check the luminous dots outside the hour markers for flaking or loss. The embossed gold numerals and markers should be crisp, not worn flat. |
| Crystal | These cases open through the crystal rather than the case back. If someone has attempted to pry the case back off, there will often be scratches or tool marks around the case back edge, which is a sign the movement may have been accessed improperly or not at all. |
| Movement | The caliber 661 is an automatic, and dried oil creates enough friction to stop the rotor and mainspring system from functioning properly on examples that have sat unserviced for years. Ask about service history. A watch that winds and runs but loses time significantly is often an oil issue, not a worn-out movement. |
| Case | The case is 10K yellow gold with a stainless steel back. Check the lugs for wear through the gold layer, and look at the case back edge for tool marks from any previous opening attempts. The swept lug style can show thinning at the tips on heavily worn examples. |
| Crown | The original waterproof rating no longer applies to any vintage watch, regardless of what Hamilton advertised at the time. Check that the crown winds and sets smoothly, and look for any corrosion around the crown tube that might suggest past moisture intrusion. |
The Movement
The caliber 661 is a 17-jewel automatic Hamilton movement that winds itself through the motion of the wearer's wrist via a rotating oscillating weight. It delivers a sweep seconds hand rather than a ticking subseconds register, which gives the watch a cleaner face and a more fluid look on the wrist. It is a capable movement when properly serviced, but the oscillating weight assembly has a reputation for being fussy to reassemble correctly during a service.