Alarm A
1971–1973 · Stainless Steel Alarm B
About the Alarm A
The Alarm A was made from 1971 through 1973 in a stainless steel case with a round profile and swept lugs. It runs on Hamilton's caliber 642, which drives both the timekeeping and alarm functions. As part of Hamilton's Alarm family, this model represents the utilitarian, workaday side of that line, stripped down to stainless steel and priced accordingly at $135.00 in 1972.
Finding one in solid condition means checking the alarm function carefully, as the 642's alarm mechanism adds mechanical complexity that doesn't always survive decades of sitting unused. Applied indices on the dial are worth examining closely for any separation or loss, and the stainless steel case tends to hold up well but will show honest wear on the lugs after fifty-plus years.
From the Catalog
Hamilton's 1972 catalog kept the description simple: stainless steel, $135.00. No extra framing, no feature list beyond the implied alarm function. At that price it was a practical choice for someone who wanted a mechanical alarm on the wrist without moving into gold-filled territory.
Hamilton Catalog Images
1971
1972
1973
What to Look For
| Dial | Look closely at the applied indices. Any separation, corrosion at the base of an index, or uneven patina around them suggests moisture got in at some point. Check the alarm hand and minute hand alignment at rest. |
| Crystal | Inspect for deep scratches or crazing. A worn crystal on a watch this age usually means it hasn't been touched in a long time, which raises questions about the movement's condition. |
| Movement | Ask about service history. Dried oil creates enough friction to stop the caliber 642 even when the watch appears to run and wind normally. An alarm complication means more parts that need fresh lubrication, so a recent service is worth prioritizing. |
| Case | The swept lugs are prone to thinning if the case has been polished aggressively. Run a fingernail across the lug tops to feel for sharp edges, which usually means the original contour is still intact. Check the caseback seal area for any corrosion. |
| Crown | The Alarm A typically has two crowns, one for time and one to set and trigger the alarm. Work both through their positions and confirm neither feels gritty or slips. A sticky alarm crown often points to dried lubricant inside the crown tube. |
The Movement
The caliber 642 is a mechanical movement with an integrated alarm function, meaning a single movement handles both timekeeping and the alarm mechanism. The alarm is powered by a separate mainspring that releases energy through a hammer that strikes a resonating surface inside the case. It requires careful lubrication throughout because both the going train and alarm train need attention during any service.