Cal. 3 is a stem winding and setting open-faced pocket watch movement produced by Robert Frères (later called Minerva) from the early 1900s through the 1940s. It was their first stem-set movement and marked a significant advance for them.
Cal. 3 spawned a range of related pocket watch movements:
| Cal. 19/3 | Open face pocket watch |
| Cal. 19/9 | Open face pocket watch |
| Cal. 19/27 | Open face pocket watch |
| Cal. 19/9 CH | Crown operated chronograph |
| Cal. 19/10 | Pusher operated chronograph |
| Cal. 19/11 | Pusher operated split seconds chronograph |