There are two entries because the two coins are assigned to different currencies.
The 1949 coin is of the Palestinian Pound (1927 to 1952) and the 1955 coin is of the Israeli pound/lire (1952 to 1980).
Although for practical purposes the currency was just renamed, these were technically two different currencies:
https://en.wikipedia.org/wiki/Palestine_pound
https://en.wikipedia.org/wiki/Israeli_pound
And so, although the coins were identical and probably share a KM# for that reason, I can understand why they have been catalogued as two separate entries on Numista.