Landing at a gun turret on board the Navy cruiser Tre Kronor. This was a routine landing spot for helicopter transports (in the early years of military helicopter trials).

The photo belongs to Marinens Pressdetalj, via the Swedish Maritime Museum's collection (published with permission). The photographer is unknown.

Parked outside hangar 81 at the F18 Tullinge Air Force Base in southern Stockholm.

A set of new military helicopter pilots in front of Ostermans' Bell 47 at the F18 Air Force Base in southern Stockholm. Ostermans trained the first military pilots before the organization got its own flight school.

A newly examined military helicopter pilot.

One of several Bell 47s in Ostermans Aero's fleet.

This photo was taken on a job for the Swedish archipelago postal flight programme. The programme was launched back in 1948, end it served to ensure that the post reached its recipients when the islands where isolated by ice during the harsh winter months in the archipelago.

Helicopters flew a regular postal route, which went from Stockholm to Gällnö, Skälvik, Ingmarsö, Stavsudda, Möja, Harö, Sandhamn, Runmarö, Nämdö, Ornö and Utö, prior to returning to Stockholm.

Ostermans Aero broke history by performing the first mail service by helicopter in Europe when the first airmail was transported from Dalarö to the lighthouse keeper at Huvudskär on 21 February 1947.

A few letters had actually been up in a helicopter the day before, as the Swedish Post Office's Senior Administrative Director Linnäs joined the very first public helicopter display and brought three letters with him, thereby becoming the first helicopter mail man in the country.

Sources:
Ostermans Aero AB (ISBN 91-631-0364-8) by Göran Wallert
Flygminnen 1 (ISBN 91-85305-20-0) by Göran Wallert
Bromma Flygplats (ISBN 91-85496-87-1) by Michael Sanz

Note: The helicopter in this photo is not fully identified, but it is believed to be SE-HAK.