Switzerland: Airmail labels 2

Here are some rare airmail labels from Switzerland intended for use on parcels.

Year: 6.1927, Ungummed.Günter Mair's catalogue no: - SWI-A-9, imperforated, intended for use on 
parcels, black/grey-blue, 4****

Year: 8.1930, Ungummed. Günter Mair's catalogue no: - SWI-A-15, imperforated, intended for use 
on  parcels, black/grey-blue, 4****

Year: 6.1931, Ungummed. Günter Mair's catalogue no: - SWI-A-16, imperforated, intended for use 
on  parcels, black/grey-blue, 4****

Year: 6.1931, Ungummed. Günter Mair's catalogue no: - SWI-A-17, imperforated, intended for use 
on  parcels, black/grey-blue, 4****