Introduced as the SW 300, Sellita soon updated the lower bridge for durability as the SW 300-1. Although many sources claim introduction as early as 2003, there is no evidence that the SW300 name existed prior to 2008. Sellita's own website only shows SW300 as of December, 2008. An updated version with improved gear profile appeared in 2008 and a new pallet bridge has been used since 2013.
Many watch manufacturers switched from ETA's 2892A2 to Sellita's SW300-1, often without advertising the change in suppliers. Today, most non-Swatch Group watch makers use this movement instead of the ETA.
All versions of Cal. SW 300 measure 11.5 ligne, feature automatic winding and a date wheel. The movement is 25.6 mm in diameter, 3.6 mm thick, 25 jewels, and is a direct replacement for the ETA 2892A2.