Automatic K-420
1961 · 10k Yellow Gold Filled · Automatic
About the Automatic K-420
Made only in 1961, the Automatic K-420 is part of Hamilton's Automatic family and runs on either the caliber 661 or caliber 667, both 17-jewel automatic movements. The case is 10K yellow Gold Filled with a round profile and hidden lugs, giving it a clean, bracelet-integrated look that was very much in step with early 1960s dress watch sensibilities. The dial carries embossed gold numerals and markers on a gold-colored background, with numerals at 6 and 12 and a sweep seconds hand. Its closest relative in the lineup is the Holden, which shares similar design DNA.
The all-gold-on-gold dial treatment is striking but also means condition matters a lot here. Embossed numerals and markers can wear at their edges, and the gold background finish is susceptible to spotting or discoloration from moisture that found its way past the weatherproof rating over the decades. Finding one with a clean, unmodified dial is the main challenge.
From the Catalog
Hamilton listed the K-420 with a yellow embossed numeral and marker dial on a gold-colored background, sold with bracelet at $100.00 in 1961. The weatherproof rating was part of the original spec, reflecting Hamilton's push during this period to build practical durability into its dress watch lineup.
Hamilton Catalog Images
1961
What to Look For
| Dial | Look closely at the embossed numerals and markers under good light. The raised edges on embossed details can show wear or flaking, and the gold-colored background is prone to spotting or discoloration if moisture ever got in. Any refinishing or repainting will flatten those embossed details noticeably. |
| Crystal | This watch opens through the crystal rather than the case back, so the crystal edge and bezel area are worth examining carefully. Scratches around the case back are a telltale sign someone tried to pry it open from the wrong side, which can cause unseen damage to the case lip. |
| Movement | The caliber 667 is used in some examples, and reassembling its train bridge requires three wheels to align simultaneously, making it a genuinely tricky movement to service correctly. A watch that winds but runs erratically or stops unexpectedly may have had an incomplete service. Ask whether it has been serviced and by whom. |
| Case | Gold-filled cases from this era can show wear through to the base metal on high-contact areas like the caseback edges and lug tops. Check those spots for any color shift or pitting. The hidden lug design also means any damage there is harder to spot at a glance. |
| Crown | The crown geometry on this case makes hand-winding awkward since only one side of the crown is easily accessible. Test the crown action yourself. It should pull out smoothly to set the time with no grinding or looseness, and the stem should seat firmly when pushed back in. |
The Movement
The K-420 was fitted with either the caliber 661 or caliber 667, both 17-jewel automatic movements that wind from normal wrist motion through a rotating oscillating weight. The 667 in particular has a reputation among watchmakers for being fussy to reassemble correctly, specifically around the train bridge where multiple wheels have to seat simultaneously. Either way, a movement this age running on original lubricants is overdue for a proper service.