Automatic K-550
1954 · Stainless Steel · Automatic
About the Automatic K-550
Made only in 1954, the Automatic K-550 is part of Hamilton's early postwar Automatic family, a line that helped establish the brand's footing in the self-winding market before the Accumatic name arrived. It runs on the caliber 661, a 17-jewel automatic movement housed in a stainless steel case with one of the more practical features Hamilton offered at the time: a hidden crown. The dial carries embossed silver numerals with luminous dots at every position and a sweep seconds hand, giving it a clean, legible look that held up well against dress watches of the era.
Finding a K-550 in honest condition takes some patience. The embossed numerals hold up well structurally, but the white dial can show age in the form of discoloration or spotting, especially near the edges where moisture gets trapped first. The hidden crown is a nice detail that kept the profile clean, but it also means the crown mechanism is worth a close look since service access required care to avoid damage to the surrounding case.
From the Catalog
Hamilton marketed the K-550 in 1954 as a shock resistant, water resistant, and anti-magnetic automatic with embossed numerals and a sweep seconds hand, positioning it as a capable everyday watch at $75.00 on strap, or $79.50 with a bracelet. The hidden crown was called out specifically in period marketing, a practical selling point that also gave the watch a cleaner profile than most of its competitors.
Hamilton Catalog Images
1954
What to Look For
| Dial | Look carefully at the white dial for discoloration, spotting, or moisture damage around the edges. The embossed silver numerals should stand crisp and even with no flaking or pitting. Check that the luminous dots are intact and haven't been touched up with mismatched material. |
| Crystal | The K-550 opens through the crystal rather than the case back. Look for scratches or chips around the crystal edge and bezel where someone may have tried to pry the case open incorrectly. A scratched-up case back is actually a red flag here, since it suggests someone didn't know how the case was designed to open. |
| Movement | Ask about service history. The caliber 661 is an automatic, and oil that has dried and thickened over decades of sitting can build up enough friction to stop the rotor or the gear train entirely. A watch that winds manually but won't run reliably on the wrist often points to this problem. |
| Case | The stainless steel case should show wear consistent with its age but look for dents or dings around the lugs. The swept lug profile is a nice period detail worth preserving, so heavy polishing that rounds off the edges is worth noting before purchase. |
| Crown | The hidden crown is a signature feature here, so make sure it pulls out cleanly through all positions and pushes back flush without sticking. A crown that sits proud of the case or feels loose may indicate a worn stem or crown tube. |
The Movement
The caliber 661 is a 17-jewel automatic movement that Hamilton used across several models in this period. It winds bidirectionally through a rotor, so normal wear on the wrist keeps it running without manual winding. The movement is serviceable but not the most forgiving to work on, since reassembling the oscillating weight carrier requires patience and a steady hand.