Cal. ST1812, produced by Tianjin Seagull Corporation, is an automatic movement with a central date wheel. The design is similar to the ETA 2892A2.
Besides finishing, there are some differences between Cal. ST1812 and ETA’s Cal. 2892A2. Cal. ST1812 uses a traditional fixed pin balance instead of the ETACHRON balance in the 2892 and has a fully slotted excentric in the regulator. The balance bridge is mounted using holes instead of pins as on the ETA. The fourth wheel on Cal. ST1812 also have six instead of eight spokes and places the winding jewel on the post bearing instead of the bridge. Some examples have an extra jewel for the barrel arbor.