Well it looks like it's back to square one in trying to find Stepling's book. A closer look at the Berlin State Library catalogue shows the Stepling volume entered under the title De Pluvia Lapidea Anni 1753 ad Strkow et ejus causis Meditatio and states "Kriegsverlust" and "keine Benutzung möglich", which according to Google Translate means "war loss" and "not possible to use".
So Robert van Gent's hunch about the availability of the book was correct. Now it's up to our Czechoslovakian readers to see if they can locate the volume in a library within the country. If anyone gets lucky, please advise, and I'll post to the list.
More to come...