Thinline 6506
1968–1970 · 10k Rolled Gold Plate / Stainless Steel · Manual Wind
About the Thinline 6506
The Thinline 6506 was produced from 1968 through 1970, part of Hamilton's Thinline family of slim-profile dress watches that defined much of the company's late-1960s American lineup. It runs on the caliber 639, a 17-jewel manual wind movement housed in a 10K yellow RGP top with stainless steel back. The dial is white with applied gold numerals at 3, 6, 9, and 12, applied gold markers filling the remaining positions, and a subseconds register at 6 o'clock. The round case and swept lugs give it a clean, unfussy profile that reads well on the wrist without demanding attention.
Applied gold indices hold up better over time than printed ones, but on a watch this age it's still worth checking closely for any that have shifted, separated from the dial, or gone missing entirely. The white dial can show yellowing or spotting depending on how the watch was stored, and finding one with an unmolested, clean dial makes a real difference. Original bracelet examples are increasingly hard to find intact, so a 6506 that comes with its period bracelet is a worthwhile find.
From the Catalog
Hamilton listed the 6506 in 1968 with a 10K yellow RGP and stainless steel back case on bracelet at $69.50, positioning it as an accessible dress watch in the Thinline lineup.
Hamilton Catalog Images
1968
1971
What to Look For
| Dial | Inspect each applied gold numeral and marker under good light. Look for any that have separated at the edges, shifted out of alignment, or gone missing. Check the white dial surface for spotting, yellowing, or moisture damage near the subseconds register at 6. |
| Crystal | Check for deep scratches, chips at the edges, or a poor-fitting replacement. A correct crystal sits flush with the bezel and doesn't rattle. |
| Movement | The caliber 639 has very little clearance between its overlapping parts, and dried oil creates enough friction to stop it entirely. Wind the watch fully and confirm it's running before assuming it just needs a service. A watch that ticks off and on, or stops under the slightest positional change, points to dried lubrication throughout. |
| Case | The 10K RGP top can show wear-through on high-contact points, particularly the lugs and the area around the crown. Check those spots carefully. The case back can be tricky to open without the right tools, so look for evidence of prying around the edge. |
| Crown | Confirm the crown pulls out cleanly and sets the time without slipping. A damaged or replaced crown is common and worth knowing about before purchase. |
The Movement
The caliber 639 is a 17-jewel manual wind movement made during Hamilton's American production era. It's a compact movement designed to fit the slim Thinline cases, which means tolerances are tight and parts sit in close proximity to one another. It winds and sets conventionally, and when properly serviced it runs reliably, but it does not tolerate neglect well.