Thin-o-matic T-416
1966–1967 · 10k YGF · Automatic
About the Thin-o-matic T-416
Made from 1966 through 1967, the Thin-o-matic T-416 is a round, 10k yellow Gold Filled automatic from Hamilton's Thin-o-matic line, which explored slimmer automatic movements during the mid-1960s. It runs on the caliber 623, a 17-jewel automatic movement, and features a silver dial with Roman numeral hour markers and a sweep seconds hand. The T-416 fits into the broader Thin-o-matic family, which has its own dedicated guide covering the line's history and development in more depth.
Dials on the T-416 can show up with black dot accents alongside the Roman numerals, so it's worth looking closely at exactly what you have before buying. Silver dials from this era are prone to spotting, foxing, and uneven aging, especially near the edges, so condition varies considerably. Finding one with a clean, unrestored dial and original case finish intact makes a real difference.
From the Catalog
Hamilton listed the T-416 in 1966 in a 10k yellow gold filled case with a bracelet option at $100 and a strap option at $89.50, positioning it as an accessible entry into the Thin-o-matic automatic line.
Hamilton Catalog Images
1966
What to Look For
| Dial | Look for spotting, discoloration, or edge damage on the silver dial. The applied indices should sit flat and even with no separation from the surface or tarnishing. Confirm whether the dial has black dot accents alongside the Roman numerals, as both versions exist and affect presentation. |
| Crystal | Check for chips, deep scratches, or crazing. A worn crystal can often be replaced, but it's a useful negotiating point and worth noting. |
| Movement | Ask when the caliber 623 was last serviced. The stem for this movement is a discontinued part that can be genuinely difficult to source, so if the crown feels loose, gritty, or doesn't engage cleanly, factor in the added complexity of that repair before purchasing. |
| Case | Gold filled cases show wear through the plating over time, particularly on the caseback, lugs, and high contact points. Look for bright brass showing through at the edges. Swept lugs are harder to rebuff without losing definition, so check those carefully. |
| Crown | Spin it, pull it, and push it back in. It should wind with smooth resistance and snap back to position cleanly. A sticky or loose crown on a 623-based watch is worth investigating before purchase. |
The Movement
The caliber 623 is a 17-jewel automatic movement produced during Hamilton's transitional period into Swiss-made movements. It winds via a bidirectional rotor and drives a sweep seconds hand, giving the watch a clean, unbroken dial. Like most movements of its age, the 623 needs fresh oil to run properly since dried lubricants create enough internal friction to stop even a healthy movement.