The connexion is that this is the Frederic who asked for the "inventory after death", cause he wasn't only King of Sweden but also Karl's successor as Landgraf of Hessen. Therefore, Karlshafen was part of his country. When F. W. von Malsburg confiscated the letters an apparatus Bessler left in his Karlshafen house, he did it being a servant of Frederic.Despite Karl the Landgrave son marrying the Swedish princess, I see no connection with Bessler’s world.
(17d Orffyreus 1 - Sicherstellung)
Adam von Mansberg was a landlord in Meinbrexen next to Fürstenberg, being an underling of the Braunschweig Karl, though at the time being in England. (JC)
So both Malsburg (Hessen) an Mansberg (Braunschweig/England) were interested in the last PM. Malsburg managed to impound the Karlshafen part of Bessler's legacy for Frederic. Mansberg wasn't able to buy the PM in Fürstenberg during Besslers lifetime. If the PM and the engravings were left in Fürstenberg, we don't know who appropriated them, probably somebody of the Mansberg family or somebody else working for the Braunschweig Karl. If Bessler in his last days brought the PM back to Karlshafen, maybe Malsburg defalcated it, or Bessler's widow hid it. Of coursealso the master himself could also have destroyed his product, if he had the time left to do so.
To me theses questions are open:
Has Karl (Braunschweig) ever shown any interest in the PM?
Is it true that the widow offered the inheritance to "the Duke" (which ist Karl, Braunschweig) as claimed in JCs book p. 160?
How could she do so, as the inheritance was impounded by the Hessians Malsburg/Frederic?