Bulgaria M51/72

A heavy Italian influence can be seen in the design of the shell and liner on the M51/72. There are variations to the shell, rivets, liner  and chinstrap etc which can be seen in the following examples. This one has the 2nd and most common pattern "Splinter" camo cover. Not to much is known about the exact year these helmets were introduced, presumably they were designed in 1951, and introduced a short time thereafter, the "72" I am guessing is the final variant of this helmet, but which  I am not sure.