R-class minesweepers in 1980's

The R class patrol boats was a class of Finnish patrol boats, originally constructed as coastal minesweepers. They were modified into patrol boats by the end of the 1960s and transferred to the Patrol Flotilla and later to the 7th Missile Flotilla. They were then used for sea patrol and as anti-submarine warfare vessels. They were stricken from the Finnish Navy list in the 1990s.

The R class was much liked in the Finnish Navy, due to their low fuel consumption and their good seagoing qualities. They were in principle unsinkable (the vessels could have a list of 115 degrees without sinking and still return to upright position).

The three later vessels, Ruissalo, Raisio and Röyttä, were somewhat larger and the vessels are therefore sometimes referred to as the Rihtniemi and Ruissalo classes. However, the Finnish Navy used the designation R class for all five vessels.
https://en.wikipedia.org/wiki/R-class_patrol_boat