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Watch movement houses

The five houses whose calibers this site documents, from the Swiss workhorse automatics to the Japanese movements that dominate the enthusiast world.

The Swiss workhorses

ETA, the Swatch Group's movement arm, makes the reference Swiss automatics such as the 2824-2 and 2892-A2 whose footprints the rest of the industry matches. Sellita builds calibers dimensioned to the ETA originals, which makes them the best-known drop-in donors.

Ronda, also Swiss, is the specialist in reliable quartz calibers found in much of the affordable Swiss-made quartz market.

The Japanese makers

Miyota, Citizen's movement arm, is one of the largest makers of mechanical calibers in the world, supplying affordable automatics like the 8215 and 9015. Seiko, through its TMI business, supplies the NH and 4R series that dominate the enthusiast and modding world.

The Japanese movements are dimensioned to their own standards, so matching a donor within a range means checking the specific footprint rather than assuming Swiss compatibility.

Why the houses matter for a swap

The whole idea of a drop-in donor grew out of these houses. When open supply of ETA movements tightened, Sellita's matched calibers became the standard alternative, and the modding world settled on the Seiko NH35 for its value.

Each maker page here lists the calibers it makes that this site documents, so a watch can be traced from its movement house to the exact donor footprint.

Using the maker pages with the tool

The maker overviews explain who makes a movement and how its range fits together, and each links straight to the caliber pages with the exact dimensions. The fitment tool then shows which movements share a footprint.

Together they answer the two questions behind any swap: what movement is in the watch, and what will drop into its place.

Related

Sources: Wikipedia: ETA SA · Wikipedia: Sellita