Welcome to the message board Stephane.
First your vase was made by Kosta rather than Kosta Boda, Kosta Boda was created later with the merger of the three companies Kosta, Afors and Boda. Your vase was designed by Vicke Lindstrand, the signature tells us this as the L in LH denotes Lindstrand and the H is the code used for a hand formed items, different letters were used for other production techniques (cutting etc). The design may date to the mid or late 1950s,
Nice vase.
John