Austria: Airmail labels

Here is a great lot of rare and early airmail labels from Austria.

Year: 23.4.1928, Gummed. Günter Mair's catalogue no: - AUT-A-1b, perforated 12 ½ , sheets of 40(4x10), transparent paper, black/light blue, 6******

Year: 3.1928, Gummed. Günter Mair's catalogue no: - AUT-A-2a, perforated 9 ½ , sheets of 126(7x18), further date: 1.1930, transparent paper, black/light blue or blue(unlisted) 4****

Year: 23.4.1928, Gummed. Günter Mair's catalogue no: - AUT-A-2b, perforated 12 ½ , sheets of 126(7x18), transparent paper, black/light blue, 4****

Year: 1928, Gummed. Günter Mair's catalogue no: - AUT-A-2c, perforated 11 ½ , sheets of 126(7x18), transparent paper, black/light blue, 4****

Year: 1.1933, Gummed. Günter Mair's catalogue no: - AUT-A-3a, perforated 12 ½ , sheets of 90(6x15), minor varieties of "F" (3 types) on same sheet, black/light blue, 3***

Year: 1937, Gummed. Günter Mair's catalogue no: - AUT-A-3b, perforated 12 ½ , sheets of 
90(6x15), black/dark grey-blue, 3***