Thinline 4006
1963–1965 · 10k Yellow Gold Filled · Manual Wind
About the Thinline 4006
Made from 1963 through 1965, the Thinline 4006 is part of Hamilton's Thinline family, a line built around the idea that a dress watch should disappear under a shirt cuff as easily as it draws attention at a dinner table. The 4006 runs on Hamilton's caliber 687, a 17-jewel manual wind movement, housed in a 10K yellow Gold Filled round case. Hamilton marketed the Thinline series heavily on its slim profile and its Weatherproof engineering, which used seals to keep dust and moisture out of the movement.
Finding a 4006 in good shape means paying close attention to the Gold Filled case, which can show brassing at the lugs and case edges after sixty-plus years. The silver dial carries embossed gold Arabic numerals at 12, 3, 6, and 9, with stick markers filling the remaining hours and a subseconds dial at 6 o'clock, and that embossed construction holds up better than printed indices when the dial has been exposed to humidity over the decades.
From the Catalog
Hamilton described the Thinline series in 1963 as offering an incredibly compact construction with a super-slim streamlined profile, and positioned each model as combining elegance with practical Weatherproof protection for its precision movement. The 4006 retailed at $89.50, bracelet included, which placed it comfortably in the mid-range of Hamilton's dress watch lineup for that year.
Hamilton Catalog Images
1963
1964
What to Look For
| Dial | Look carefully at the subseconds register at 6 o'clock for hairline cracks or separation around the edges. The embossed gold numerals are relatively durable, but check for any flaking or discoloration near 12 and 6 where moisture tends to collect if the Weatherproof seals have failed over the years. |
| Crystal | Original crystals on Thinline models were acrylic. Check for deep scratches or a hazy, yellowed appearance that can't be polished out, which usually means replacement is needed before the watch is really wearable. |
| Movement | The caliber 687's click spring is prone to dislodging during cleaning. Ask whether the watch has been serviced recently and by someone familiar with this movement. Dried oil in a movement this age creates enough friction to keep it running poorly even after a basic cleaning without full re-oiling. |
| Case | Inspect the lugs and case back edge for brassing, where the gold-filled layer has worn through to the base metal. Light wear on the case back is normal, but heavy brassing on the lugs changes the look significantly. Also be aware that the case back can be tricky to open without the right tools, so check whether it shows evidence of being pried rather than properly opened. |
| Crown | Pull the crown gently and confirm it moves through winding positions smoothly without slipping. A worn crown tube on a watch this age can cause the crown to feel loose or sit off-center, which also compromises what remains of the Weatherproof seal. |
The Movement
The caliber 687 is a 17-jewel manual wind movement that Hamilton used across several of its slim dress models in the early 1960s. It winds from the crown, keeps time via a traditional lever escapement, and displays seconds through a dedicated subseconds dial rather than a central seconds hand, which suited the thin-profile design of the Thinline series. It's a capable movement when properly serviced, but like most movements of its era, it needs fresh oil and a thorough cleaning to perform reliably after decades of sitting.