Munchen Ta Germany Cancel 1939 "Hauptstadt Der Bewegung"

I picked this cover up last week from stamps2go. It is a really unique cover having the history of William Randolph Hearst and San Simeon Ca. The cancel is a celebration of the Hitler-Ludendorff Putsch when the Nazi's tried to take control of Germany. However it is the "TA" I'm wondering about. Does this mean it is a Telegraphenamt cancel?

Yep.

Is the use of a telegraph office cancel unusual or were all or most of the special cancels marked this way?

I wouldn't say they're rare, but they're not terribly common. It's largely a function of there not being many telegraph POs compared to regular POs. I don't recall where I read this, but I believe there were only 10-12 in Germany by war's end.

Thanks PostmasterGS. Munich being the capitol of Bavaria always had a Telegraph office. It makes sense it would be part of the post office. The postmark was Christmas night (10 PM). It would have been the only office open.

I don't see nothing that special on the cover. It's a normal airway letter to a prominent person, Mr. R. Hearst, who would receive many letters from abroad.
The pm (IMO) has nothing to do with the 1924 Munich Pustch. Munich, like other cities, as Nuremberg, where the nazi party began, was named "Haupstadt der Bewegung", that is "Capital city of the moviment" (nazi party).
As for the telegraph; perhaps, as already said, it was the only P.O. open on Xmas Day in Munich

Nice cover with an interesting historical context. Find a few more similar covers and it would be a really interesting display.