I do not have catalogs or information about these stamps, but I can provide you with some geographical information.
Ada-Kaleh was an island on the Danube river near the city of Orsova.
The Turkish name Ada Kale translates as Island Castle.
Until WWI, it was under the administration of the Turkish Empire and the Austro-Hungarian Empire, being part of the BANAT province.
After WWI, the province of Banat was divided between Romania, Serbia and Hungary.
Temesvaru postal cancellation written in Cyrillic letters refers to the city of Timisoara (currently in Romania)
Due to the construction of the hydro dam on the Danube, Portile-de-Fier I (Iron Gates I), the island of Ada-Kaleh was covered by water like several other towns on the sides of the Danube.
I found on a website an envelope with stamps with a similar overprint (or not):