The Longines 501 is a mechanical watch movement with a unique feature of a strangely minute wheel and automatic transmission wheel running on ruby studs. The day and date change of this movement are independently adjustable, although the manufacturer's method is unknown. It is suggested to adjust the day change slightly later than the date change, enabling the date to advance without affecting the day of the week, particularly useful for months with less than 31 days. Additionally, this movement possesses the functions of automatic winding, a sweep second hand, and day and date settings that can be adjusted by changing the 21-24h and 20-24h positions respectively. The Longines 501 movement was typically used around the period of 1970.