The Finnish national insignia was born on 2 March 1918, when large blue swastikas were painted on the wings of a Thulin typ D monoplane. These milleniums old good luck emblems of Indian origin meant the same for the donor, Swedish count Eric von Rosen. Four days later this plane arrived to the army of the white forces in Finland.
The commander of the above-mentioned army, General Carl Gustaf Emil Mannerheim informed the troops in his order of the day No. 26 dated 18 march 1918:
All troops are now informed that our aircraft will use from now on as a recognition mark the following sign (swastika) in blue colour on the wings and fuselage, in addition a red flag with a yellow cross will be attached to the tail.
Lack of more precise application instructions led to many different kinds of insignias appeared on the aircraft. The registration markings of the aircraft faced the same phenomenon.
On 9 May 1927 a new serial number system was introduced, being still in use. The letter combination derived from aircraft's name informed which particular type was in question. The numbers run for each type consecutively. As time went by various types of lettering appeared on the aircraft.
All variation of the national insignias and registrations markings were put to an end on 20 March 1934, when new permanent markings of the Finnish military aviation SIP IV BA2 were issued.
(Kalevi Keskinen, Kari Stenman : Suomen ilmavoimien historia 23 - Sotamaalaus - Suomen Ilmavoimien Maalaukset ja Merkinnšt 1939-45, Espoo 2003, ISBN 951-98751-6-6, ss. 3-4)