Sea Birds of Mare Balticum

I am not able to give time to my blog, being busy on the personal front I have to stay away from my hobby. However, today I present a cover received from Estonia.

The cover has 4 stamps of the sea birds of Mare Balticum, I am surprised that the stamps are of the year 1992 ! One more stamps of a whale (definative?) has been used at the left side to balance the postage.