Thin-o-matic TM-2600
1968–1970 · 14k Solid Yellow Gold · Automatic
About the Thin-o-matic TM-2600
Running from 1959 through 1962, the Thin-o-matic TM-2600 is part of Hamilton's Thin-o-matic family, which brought automatic, slimmed-down styling to American watch buyers at the turn of the 1960s. The TM-2600 is cased in 14k solid yellow gold with a round case and straight lugs, carrying Hamilton's caliber 626, a 17-jewel automatic movement. The white dial with applied stick markers and center seconds keeps the face clean and uncluttered, which suited the ultra-thin aesthetic Hamilton was promoting across the line.
Solid gold cases on Thin-o-matics tend to show their age honestly, so the first thing worth assessing on any TM-2600 is how much metal remains on the case edges and lugs. The white dial can yellow or develop spotting over time, and finding one with a clean, unrestored dial makes a meaningful difference in what the watch looks like on the wrist. The applied stick markers are worth a close look too, since loose or missing indices are common on dials this age and not always easy to replace faithfully.
From the Catalog
Hamilton's 1968 catalog listed the TM-2600 as an ultra-thin 14k yellow gold model at $195, grouping it among designs described as handsome and contemporary, with self-winding movements and full weatherproof construction.
Hamilton Catalog Images
1968
What to Look For
| Dial | Look carefully at the white dial for yellowing, spotting, or moisture damage. Check each applied stick marker to confirm none are separating, tilted, or missing. Even small shifts in the indices are noticeable on a clean, minimal dial like this one. |
| Crystal | Confirm the crystal is sitting flat and sealed properly. Cracks or deep scratches in an older crystal are common and worth factoring in, as a replacement will need to fit the slim case profile correctly. |
| Movement | Watch the seconds hand for any inconsistency in sweep. The cannon pinion on movements this age is prone to loosening over time, which can cause the hands to slip or the watch to appear to run slow even when the movement is otherwise healthy. A recent service is worth asking about. |
| Case | 14k solid gold cases wear differently than gold-filled, but they still show polishing and wear at the lugs and case edges. Examine under good light for deep scratches, over-polishing that has softened the original lines, or any cracks near the lug roots. |
| Crown | Test the crown for smooth engagement in both winding and setting. Check that the watch is not being sold as weatherproof for modern use. Original weatherproof ratings do not translate to actual water resistance in a watch of this age, and the seals have almost certainly degraded. |
The Movement
The caliber 626 is a 17-jewel automatic movement built around a conventional full rotor, giving it reliable winding without the complexity of the micro-rotor designs used elsewhere in Hamilton's catalog at the time. It runs at a steady rate when properly serviced and is a relatively straightforward movement for a watchmaker familiar with Hamilton automatics of this era. Lubricants in any caliber 626 this age will have dried or degraded, so a movement that has not been recently serviced should be treated as overdue regardless of how well it appears to run.