Cal. 27 is a 19 ligne stem winding and setting open-faced pocket watch movement from Robert Frères (later called Minerva). It was descended from Cal. 19/3, the company’s first stem-set movement, and shared many features. It also shares its basic design with Cal. 19/9. Cal. 27 was introduced around 1908 and remained in production through the 1940s.
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 |