The most blatant self-authenticating claim, and the one that is so starkly utter nonsense, with zero support from Scripture and even common sense, is that they were appointed in 1919 as "the faithful and discreet Slave".
And hence that claim to Authority and some sort of "Hot Line to Heaven" can be claimed by today's Governing Body.
The 1919 claim relies on the long debunked 1914 nonsense, and upon claiming that Jesus chose them on the basis of what they were teaching circa 1919. As Raymond Franz said in one of his Books, that claim is " an Insult to Jesus".
A common sense reading of the Parable that the FDS comes from makes it plain it is ONLY a Parable, a Teaching Aid, a Story, and not a prophecy of any kind.
Hence the Governing Body today are :
Self-appointed Charlatans.