It would be more accurate to say "one of the world's first postal cards," since three different cards were issued in Austria-Hungary on 1 October 1869. The cards shown above are both examples of Austria #1 (I'm using Ascher's numbers; Higgins & Gage are the same, I believe). The defining characteristics of this card are the Austrian coat of arms and German text, including notes at the top and bottom of the back. These notes distinguish #1 from cards with an identical front that were issued in later years.
The other two cards issued on the same day are Hungary #1 and #2. Hungary #1 is identical to Austria #1, except that it has the Hungarian coat of arms on it, rather than the Austrian. Hungary #2 is identical to Hungary #1, except that the text is in Hungarian, rather than German.
I got a nice exemplar of Hungary #1 at WESTPEX yesterday. The dealer had several in one of his $5 boxes, but this was the earliest that I found, postmarked in Karlstadt (now Karlovac, Croatia) on 20 October 1869, only 19 days after the introduction of the postal card. The writer was requesting prices for cotton yarn from a firm in Vienna.