Thin-o-matic T-413
1965–1969 · 10k YGF · Automatic
About the Thin-o-matic T-413
Made from 1965 through 1967, the Thin-o-matic T-413 is part of Hamilton's Thin-o-matic family, a line built around slim, elegant automatics designed to compete with the dressiest Swiss offerings of the era. The case is 10k yellow Gold Filled, round, and just 10mm thick, giving it a genuinely svelte profile on the wrist. Power comes from the caliber 623, a 17-jewel automatic with a sweep seconds hand. While most Thin-o-matic models of this period used a Buren micro-rotor movement, the 623 is a different animal, worth understanding before you buy.
Finding a T-413 in honest condition means paying close attention to the Gold Filled case, which can show wear through to the base metal at the lugs and case edges after six decades. The white and silver dial with applied gold markers holds up well when it hasn't been exposed to moisture, but any sign of separation or corrosion around the markers is worth flagging. The hidden lug design looks sharp but makes it harder to evaluate lug condition at a glance, so look carefully.
From the Catalog
Hamilton listed the T-413 in 1965 at $100 on bracelet and $89.50 on strap, positioning it as an accessible entry into the Thin-o-matic line in a 10k yellow gold filled case.
Hamilton Catalog Images
1965
1966
1968
What to Look For
| Dial | This is a white and silver dial with applied gold markers. Check for separation or detachment at the markers, which is common when moisture has gotten inside. Any browning, spotting, or corrosion near the edges should factor into your assessment. |
| Crystal | These came with acrylic crystals. Scratches are expected and easily polished out, but a deeply gouged or cracked crystal should be replaced before the watch is worn. |
| Movement | Ask when the caliber 623 was last serviced. The stem for the 623 is a non-standard part that was discontinued long ago, so a broken or damaged stem can become a sourcing headache. Confirm the crown engages cleanly and the watch winds and sets without resistance. |
| Case | 10k yellow gold filled cases from this period show wear at the lugs and high contact points first. Look for any brass showing through the gold layer. The case back can be tricky to open without the right tool, so don't let amateur case back damage pass without comment. |
| Crown | Check that the crown pulls out to the setting position smoothly and snaps back without drama. This watch is not suitable for water exposure regardless of its original weatherproof rating, so a tight crown matters for dust protection at minimum. |
The Movement
The caliber 623 is a 17-jewel automatic made for Hamilton during the Swiss production era. It uses a conventional full rotor rather than the micro-rotor found in many other Thin-o-matic models, which gives it a more standard thickness profile despite the slim case. It's a solid, serviceable movement, but dried lubricants after this many years can create enough friction to stop it entirely, so regular service is not optional.