Like the 2824 and 2836, Cal. ST2100 measures 11½ ligne (25.6 mm) in diameter. Cal. ST2130 (date only) is 4.6 mm thick, while Cal. ST2100 (day/date) is 5.05 mm thick.
The Valanvron VAL-24 and STP1-11 are thought to be based on this Chinese ebauche. Both share the same architecture (nearly identical to the ETA 2824) and there is much circumstantial evidence that both companies use this base. For example, photos on the STP web site include the label, “ST2100” under the movement, and bot appear to use pinned holes like Sea-Gull rather than trepanned studs like ETA and Hangzhou. If this is the case, Valanvron and STP must reassemble the movement in Switzerland and add more than 50% value to the movement so it can legally be called Swiss Made.