I think it would be the best to go to the forum "Thüringen".
Leutenberg is existing in Thüringen. It belonged in the 1900s to the principality of Schwarzburg-Rudolstadt, one of the funny small states in Thüringen(75.000 inhabitants in 1871).
I think your chances to find anything there will be better than in Mecklenburg.
May be this Leidenberg is that one situated in Bavaria. This is not so far away from Thürigen.