Cal. SW285-1 M a is a hand-winding movement with moon phase, day/night indicator, and date from Sellita. Like other Sellita SW200 movements, it is based on the design of the ETA 2800 family, though ETA does not sell a direct competitor with the same functions. Sellita has produced this movement since 2019. Cal. SW285-1 a is an automatic version.
The moon phase is indicated using a disc located at 6:00 on the dial and the date is located at 3:00. The day/night indicator is a pointer in a subdial at 10:00. This is very similar to Cal. SW285-1 M b, which differs in that it uses a disc for the day/night indicator.