The Hamilton Jazzmaster Open Heart Auto 42mm (H32705551) is the larger Open Heart, with a silver dial that is partly openworked to show the balance wheel. Hamilton’s official page lists a 42 mm stainless steel case, 11.44 mm thick and 50 mm lug to lug, with 22 mm lug width, a sapphire crystal with anti-reflective coating, an open case back and 50 m (5 bar) water resistance. The H-10 automatic caliber provides an 80-hour power reserve, and the watch is on a calf leather strap.

Owners and buyers praise the elegant design and the quality of the finishing of the Open Heart line. A long-term owner on Dialicious reports no breakdowns in over ten years, and the recurring complaint is that silver hands are hard to read against the silver movement below. One buyer on a Swiss retailer site notes that the 40 mm and 42 mm models have different strap quality and no quick-release.

Hamilton’s official page marks this reference as past collection, so it is no longer in current production, although retailer stock may remain.