Automatic K-300 cld
1954–1955 · 10K yellow · Automatic
About the Automatic K-300 cld
Made from 1954 through 1955, the Automatic K-300 cld is part of Hamilton's early K-series automatic lineup, a group of round-cased automatics that helped establish the brand's presence in the self-winding market during the mid-1950s. It runs on the caliber 661, a 17-jewel automatic movement, and comes in a 10K yellow gold case with a stainless steel back. The cld suffix indicated a sealed case design: the crystal was set into the bezel on a gasket, the bezel seated against the case with a second gasket, and the crown used a two-piece stem with its own gasket sealing at the stem tube. Not waterproof — Hamilton's waterproof line came later in the decade — but meaningfully sealed against moisture and dirt in a way standard cases of the period weren't. The dial features applied gold numerals and applied gold markers, with numerals running from 6 to 12, and a sweep seconds hand. Hamilton offered it in two dial options: plain silver or black.
Applied gold details on dials from this era are worth scrutinizing closely, as the adhesive can fail over decades and individual numerals or markers can lift, shift, or go missing entirely. The silver dial version turns up more often than the black, so finding a clean black dial example in solid shape is genuinely satisfying. Either way, look for a dial that shows honest wear rather than signs of refinishing, since a relumed or repainted dial will flatten the collectibility considerably.
From the Catalog
Hamilton described the K-300 cld as having a natural gold case with a stainless steel back, 18K gold luminous markers on a choice of plain or black dial, sweep seconds, and features including water resistance, shock resistance, and anti-magnetic protection. It retailed for $115.00 in 1954, placing it firmly in Hamilton's premium automatic tier for the period.
Hamilton Catalog Images
1954
1955
What to Look For
| Dial | Check each applied gold numeral and marker individually. Any that are lifted, tilted, or absent are difficult to correct without professional help, and replacements that match the originals are hard to source. The luminous material on the markers will have aged and likely discolored, which is normal and expected. Refinished dials often show a slightly too-uniform surface or inconsistent lume color, both signs the dial has been touched. |
| Crystal | The K-300 cld uses a domed acrylic crystal typical of the era. Scratches and hazing are common and can generally be polished out, but deep gouges or crazing mean replacement. Also worth knowing: on some Hamilton round-case models from this period, the case opens through the crystal rather than the case back. If the case back shows pry marks or scratching around the edge, someone may have been trying to open it from the wrong side. |
| Movement | Oil dries out in stored automatics, and the caliber 661 is no exception. A watch that starts only with a shake and then stops, or that runs erratically and then quits, is telling you it needs a full service before anything else. If the rotor spins freely and the watch winds down quickly, that can also point to a worn or slipping mainspring. Budget for a service on any example that hasn't been recently cleaned. |
| Case | The case is 10K yellow gold with a stainless steel back, so inspect the gold surfaces for deep dings or polishing that has rounded off the original lines. Light wear on the case back is fine, but the stainless back should seat and seal properly. If it looks like it has been forced or pried, check the gasket area and the seal. |
| Crown | The crown should screw or pull out cleanly through each position without slipping. A crown that spins loosely or doesn't engage the setting position is a common wear point and usually means a replacement crown or worn stem, both fixable but worth noting before purchase. Also keep in mind that even though this watch was originally described as water resistant, no vintage watch of this age should be trusted near water. |
The Movement
The caliber 661 is Hamilton's 17-jewel automatic from the mid-1950s, a competent self-winding movement that winds via a bidirectional rotor. It keeps reasonable time when properly serviced and is a solid, workmanlike automatic rather than a high-complication movement. Getting the oscillating weight carrier properly reseated during service is one of the fussier steps, so this is not a movement to hand to a watchmaker unfamiliar with vintage Hamilton automatics.