There is another Augstenberg in the Silvretta.
And another one much closer, on the Swiss-Austrian border between Naafkopf and Schesaplana. This other one is also known as Tschingel.
There is a large summit cross, but according to my altimeter, my eyes and the Swiss Topo map, the actual summit is about 250m further to the south, and 6m higher.
I guess the fact that the summit cross would be invisible from Malbun if it were on the real summit plays a role here ...