This is obviously an ETA 2824 clone, just like the Sellita SW200, and based on the release notes Steinhart has contracted the component manufacture to companies in Switzerland. I would assume that's a production stamp of some sort.
Hi, I think it's great news that Steinhart will start to produce its own movement, STEINHART ST.5. I'll also believe that it's based on or better say modified copy of ETA 2824-2