To contribute to this topic...

In the book "Hladno oružje Srbije, Crne Gore i Jugoslavije 19-20 vek" (Melee /cold (steel) weapons of Serbia, Montenegro and Yugoslavia 19th-20th century) by Branko Bogdanović, you can find this lovely illustration (page 143):

Yugoslav M51 knife Yugoslav M51 knife

And on pages 48-49 the text says that after WW2, hand to hand combat got special attention and was under Soviet influence. At the beginning of the 1960s, the Army got a new homemade knife (kama) M.1951 (j), based on the Soviet army knife (NR)40.
The price of a single M51 knife was 25 dinara (cca 7 DEM), according to a price list from 1.7.1970.
It was meant for the soldiers (fighters) belonging to scout, saboteur and paratrooper units.
Its fiery baptism was 4 decades after being made (by then regarded as old, and mostly given to units of the Territorial defense - Teritorijjalna obrana /TO/), in the hands of the enemy of the Yugoslav People's Army (JNA).
During a brief conflict (The Ten-Day War), in June 1991, the Territorial defense issued this knife to all soldiers/fighter who were issued the M56 submachine gun - because of lack of M56 bayonets

The last paragraph mentions a navy knife with a braid for the knife ("nož mornarski sa gajtanom za nož") and a brief description.

*I added some information purely for a better understanding and context. All of this can be verified in the book.

Yugoslav M51 knife Yugoslav M51 knife

I thought more info could be useful for other collectors.

Kind regards

P.S. This thread has nice pictures of the M51 knife: Yugoslavian fighting knife.