What Is an Open-Heart Watch?
An open-heart watch is a mechanical timepiece with a window cut into the dial, revealing the balance wheel — the oscillating component that regulates timekeeping. It's the visual proof that you're wearing a living, breathing mechanical instrument. Every tick you see through that window is the escapement releasing a tiny packet of energy from the mainspring, translated into the movement of the hands.
Open-heart watches sit between standard automatic watches (fully covered dial) and skeleton watches (where most of the movement is visible through extensive dial and plate cut-outs). The open-heart approach is more subtle: a single window, usually at 12 o'clock, that reveals just enough to be captivating without sacrificing legibility.
How the Balance Wheel Works
The balance wheel is a weighted wheel that oscillates back and forth at a constant rate — typically 21,600 times per hour (3 Hz) or 28,800 times per hour (4 Hz). Each oscillation allows one tooth of the escape wheel to advance, which in turn moves the gear train and the hands. The precision of this oscillation determines the accuracy of the watch. When you look through an open-heart window, you're watching the most critical component of the entire movement do its work in real time.
Why the NH38A Is the Ideal Open-Heart Movement
The Seiko NH38A is the same calibre as the NH35A but without the date complication. This matters for open-heart designs: removing the date wheel and disc creates more space for the dial window and allows a more symmetrical, balanced dial layout. The NH38A offers the same 41-hour power reserve, hacking, and hand-winding capability as the NH35A (read our NH35A movement guide for full specs), but in a format optimised for dial designs that prioritise aesthetics over date functionality.
The CrownCraft ROADSTER
The CrownCraft ROADSTER uses the NH38A with an open-heart window at 12 o'clock, finished in rose-gold tones. The warm sunburst dial and rose-gold PVD case create an opulent look that contrasts with the industrial honesty of the exposed movement. The name reflects the philosophy: like a sports car with an exposed engine, the ROADSTER makes the mechanical heart visible.
At €259, the ROADSTER delivers a genuine open-heart complication with sapphire crystal, rose-gold finishing, and the NH38A movement. Most open-heart watches at this quality level start at €400+.
Open-Heart vs Skeleton Watches
Skeleton watches remove material from the movement plates themselves, making the entire mechanism visible from both sides. They're more dramatic but often harder to read and more fragile. Open-heart watches keep the full movement plate intact and simply add a window in the dial — better legibility, more practical for daily wear, and mechanically identical to a standard automatic.
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