Straits Settlements: Airmail labels 3

Here are more old airmail labels from Straits Settlements.

Year: 1930, Ungummed. Günter Mair's catalogue no: - STS-A-2a, perforated 12 and rouletted, sheets of 30(3x10),  ref.: "P . & T .-Mail 25", black/dark blue-grey, 5*****

Year: 1931, Gummed. Günter Mair's catalogue no: - STS-A-3b, rouletted, sheets of 30(3x10), 3mm between 2. and 3. line, ref.: "P. & T.-Mail 25", black/greenish grey-blue, 4****

Year: 1.6.1931, Gummed. Günter Mair's catalogue no: - STS-A-4a, rouletted H, perforated V 11,
sheets of 18(3x6), ref.: "P . & T .-Mail 25", black/greenish grey-blue, 4****