Thin-o-matic T-408
1963 · 10k YGF · Automatic
About the Thin-o-matic T-408
Made only in 1963, the Thin-o-matic T-408 is a round, 10k yellow Gold Filled automatic wearing a silver dial with Arabic numerals at 12, 3, 6, and 9, and dot markers filling in the remaining hours. The T-408 is part of Hamilton's Thin-o-matic family, which used the micro-rotor caliber 620 to keep the overall profile genuinely slim. Sweep seconds and a clean, understated dial layout give it a quietly dressy character that works well against a suit cuff.
A vertically textured dial variant exists alongside the standard silver dial, and that texture is worth paying close attention to on any example you're evaluating, since the finish can show wear or buffing damage that's easy to miss in low-light photos. The Gold Filled case held up reasonably well over the decades, but check the lugs and high-contact edges for wear-through to the base metal, which is common on any Gold Filled piece that saw daily use.
From the Catalog
Hamilton offered the T-408 in 1963 with two wearing options: on a bracelet at $95.00 or on a strap at $85.00, with the case described simply as 10k yellow gold filled. The pricing put it in the accessible middle of the Thin-o-matic range, making the slim automatic format available without stepping into solid gold territory.
Hamilton Catalog Images
1963
What to Look For
| Dial | Look carefully at the texture on examples with the vertical texture variant. Buffing or aggressive cleaning can flatten or streak the surface in ways that are permanent. Check that the Arabic numerals at 12, 3, 6, and 9 are crisp and that the dot markers haven't faded unevenly. |
| Crystal | These left the factory with acrylic crystals. Check for deep scratches, crazing, or a poor-fitting replacement that gaps at the edge. A well-fitting acrylic can be polished if the scratches are surface-level. |
| Movement | Ask when the caliber 620 was last serviced. Oil in a movement this age thickens and loses its ability to protect, and dried lubricant alone can generate enough friction to stop the movement entirely. The micro-rotor is also worth asking about specifically, as it can ride up its axle and contact the case back if the pivot has worn. |
| Case | This is a 10k yellow gold filled case, so wear-through to the base metal is the main thing to check. Run a fingernail along the lug edges and the high-contact areas near the crown. Moderate surface wear is normal and expected; worn-through plating is a different matter. |
| Crown | Check that the crown screws in or seats fully and that winding feels smooth without grinding or slipping. A worn crown or stem affects daily usability more than most people expect. |
The Movement
The caliber 620 is a 17-jewel automatic built around a micro-rotor, meaning the winding weight is integrated into the movement plate rather than sitting on top of it like a conventional rotor. That design is what makes the Thin-o-matic line genuinely thin rather than just marketing-thin. It's a capable movement that keeps good time when properly serviced, though the many small parts and the micro-rotor's tendency to ride up its axle over time mean it rewards an experienced hand at the bench.