Thank you for posting the photo. This clock is not the made by the Siegmund Stockburger in St. Georgen that I mentioned. As you have discovered, this is a modern clock with a Hermle movement.
There are a whole series of modern clock, barometers and hygrometers marked Stockburger which you can see if you google the name. It is not at all clear to whom the name belongs. I think it may not be a manufacturer's name, rather a trade name for a series of clocks etc. made to order for alrge distributor. All the instruments I have seen are marked 'Made in Germany' so it may well be a German company making these items (and maybe buying the parts from other makers, such as Hermle) for a large wholesaler who markets them under the Stockburger brand.
This my supposition - others may have better knowledge.
JTD