Blancpain has marked the 70th anniversary of its Ladybird collection with the Lady B, a spherical mechanical watch measuring just 19mm in diameter and 13.20mm thick, for a total case volume of 2.9 cm³. It is available in polished stainless steel or 18k red gold, and it runs on the Manufacture’s Calibre 615, an automatic movement measuring 15.70mm by 3.90mm. The piece takes its cue from the original Ladybird Bullet, whose strap threaded directly through a slot in the case back rather than attaching via conventional lugs.
Case construction: building a sphere around a round movement
The engineering problem here is straightforward to state and hard to solve: how do you wrap a mechanical movement in a case that reads as a sphere on the wrist, rather than as a puck or a barrel. Blancpain’s answer is a two-part case construction where the back is designed to sit almost invisibly against the skin when worn, minimizing the visual break between the case band and the underside of the watch. There are no lugs in the traditional sense. Instead, the strap passes directly through an opening machined into the case back, a direct engineering descendant of the slot-and-strap system used on the 1950s Bullet reference, which allowed the original wearer to swap straps in seconds without tools.
That absence of lugs is not a stylistic flourish. It is the only way to preserve the sphere. Conventional lug horns would break the curvature at the 12 and 6 o’clock axis and turn a round jewel into something more architectural and less organic. By routing the strap through the case itself, Blancpain keeps the geometry continuous. The trade-off is that strap changes now depend on a machined channel rather than a spring bar, which is a deliberate return to the original Ladybird’s mechanism rather than a modern quick-release solution.
Fitting a 180-component movement into 15.7mm
Inside sits the Calibre 615, based on the 7135, first introduced in 1995 and refined over three decades with updates including a silicon balance spring. It is an in-house automatic movement built from 180 components, including 29 jewels, running at 21,600 vibrations per hour with a 38-hour power reserve. At 15.70mm by 3.90mm, it counts among the smallest round automatic calibers Blancpain currently produces, and the Lady B’s case is built directly around those dimensions rather than the reverse. The movement drives hours and minutes only. There is no date, no seconds hand, no complication competing for space on the dial, which is the correct decision given how little real estate a 19mm case leaves for anything beyond legible time display.
Legibility in a case this small is not a given. Blancpain addresses it with an opaline dial fitted with gold-applied polished stick indices and hands, executed in either steel or gold depending on case material, with the steel version using grey gold hardware and the red gold version using red gold hardware. The polished, applied markers do the work that a printed dial cannot at this scale: they catch and redirect light rather than relying on contrast alone, which matters enormously once dial diameter shrinks toward the point where printed minute tracks would blur together.
Wearability and the double-tour strap
With no lugs to anchor a standard strap, Blancpain fits the Lady B with an interchangeable double-tour calf leather strap, 10mm wide, closed with a pin buckle matching the case metal. The strap is offered in seven colors: white, beige, mocha, burgundy, blue, coral and purple. Because the strap threads through the case back rather than attaching at fixed lug points, swapping colors is fast and doesn’t require tools, echoing the quick-change function Blancpain’s 1950s advertising once used to sell the original Ladybird as a “technical miracle” at 11.85mm.
The double-tour construction also does ergonomic work that a single-pass strap could not. Wrapping twice around the wrist stabilizes a case that has no lugs to resist rotation, keeping the dial oriented correctly during wear rather than letting the sphere spin loosely on a single strap pass. Water resistance is rated to 30 meters, consistent with a piece built for jewelry-watch wear rather than active use.
What the trade-offs reveal
Every decision in the Lady B traces back to the same constraint: preserve the sphere, and everything else must adapt. Finishing is simplified to opaline dial and polished applied markers rather than a multi-level dial construction, because a spherical case punishes complexity. The movement’s small footprint dictates the case’s inner dimensions rather than styling driving movement choice. And the strap-through-caseback system exists specifically because conventional lugs would have broken the curved geometry that defines the piece.
The Lady B enters Blancpain’s permanent collection in steel or 18k red gold, giving the brand a standing answer to a design problem it first tackled seven decades ago: how to make a fully mechanical watch small and round enough to function as jewelry without abandoning the movement architecture that makes it a Blancpain in the first place.
