Automatic K-506
1955–1956 · Stainless Steel · Automatic
About the Automatic K-506
Made from 1955 through 1956, the Automatic K-506 is part of Hamilton's K-series automatic lineup and runs on the caliber 661, a 17-jewel automatic movement. The case is stainless steel in a round profile, and the dial pairs embossed silver numerals at 12, 3, 6, and 9 with luminous markers and dots filling out the rest of the hour positions. A sweep seconds hand completes the layout. Hamilton marketed this one as shock resistant, anti-magnetic, and waterproof, and it was offered either on a bracelet for $75.00 or on a strap for $72.50.
Embossed dials from this era can be fragile, so look closely at the numerals and markers for chips, separation from the base, or discoloration before buying. The luminous material on the markers also ages in its own way and ranges from creamy ivory to darker patina depending on how the watch was stored. Finding a clean, unpolished example with the original dial intact is the real benchmark here.
From the Catalog
Hamilton's 1955 catalog described the K-506 as a stainless steel automatic with sweep seconds, embossed numerals, and luminous markers, emphasizing its shock resistance, anti-magnetic properties, and waterproof construction. It listed at $72.50 on a strap or $75.00 on a bracelet.
Hamilton Catalog Images
1955
1956
What to Look For
| Dial | Check the embossed silver numerals and markers carefully. Any chipping, separation, or flaking around the raised elements is hard to repair and affects value. Also look at the luminous material on the markers and dots, which can discolor or flake over time. |
| Crystal | On this model, the case opens through the crystal rather than the case back. Look for scratches or pry marks around the crystal edge, which are a sign that someone attempted to open the case from the wrong side. |
| Movement | Ask about service history. A caliber 661 that has been sitting unserviced for years can have oil that has dried and thickened enough to create friction and stop the watch from running. A properly serviced example should wind, set, and run smoothly. |
| Case | Look at the lugs and case surfaces for signs of polishing. The original brushed or satin finish on stainless steel cases is often lost to overzealous cleaning. Crisp lug edges and an unpolished case are a good sign. |
| Crown | Make sure the crown screws or seats properly and that the stem engages cleanly when setting the time. A loose or sloppy crown can indicate a worn stem or damaged threads. |
The Movement
The caliber 661 is a 17-jewel automatic movement made by Hamilton. It winds itself through the motion of the wrist via a rotating oscillating weight, which means no hand-winding is needed in daily wear, though the crown still sets the time. It's a compact, dependable movement that responds well to a proper service but can be finicky when the oil has aged and the rotor assembly needs careful reassembly.