STP5-15 is an open heart hand winding watch movement from Swiss Technology Production. It is based on Cal. STP1-11, itself a clone of the popular ETA 2824-2. STP uses a longer, thinner mainspring, boosting power reserve to 44 hours. It also includes an extra jewel on the barrel arbor.
Like other movements in the STP1-11 family, it uses a screw-type regulator with two “jaws” for adjustment. However the screw is not used in the skeletonized versions, with the “jaws” left open and an index inscribed on the opposite bridge.
STP may have used an ebauche from Sea-Gull in China to build the STP1-11 family. Photos on the company web site previously included the label, “ST2100”, which is the identifier found on the Sea-Gull ST2130 movement. The same has been said of the Valanvron VAL-24. Due to their Swiss content and finishing, STP can legally classify these movements as “Swiss Made”, and the company may now construct most or all of the movement in-house.
Cal. STP5-15 is a similar automatic movement.
The movement can be manually wound with the crown in position 1. Rotate the crown clockwise to wind the mainspring.
The time is set with the crown in second position (pulled all the way out). Rotate the crown clockwise to advance the minute and hour hands and counter-clockwise to turn them backward.