Oy Fenno-Alga Ab (Oy and Ab are abbreviations for Ltd. in finnish and swedish, respectively) was a subsidiary of the Swedish publisher Alga, and existed in Finland in the 1970's. Before and after, games were published under the Alga brand in Finland.
The vast majority (possibly all) of Fenno-Alga's games were almost identical but localized versions of Alga games already published, or being published at the same time in Sweden.
The Fenno-Alga logo was the same red "roundel" that Alga used, but with a semicircular "Oy Fenno Ab" text added above it. Indeed, the standard Alga logo can sometimes be found on Fenno-Alga games - on the game board, inside the box lid, etc.