Pisces sign appears on a postage cancel marking the monthly philatelic fair, which took place at Dizengof center, Tel aviv, in 6.3.2007. According to the Hebrew calendar March falls on the month of Adar whose sign is Pisces.
Why two fishes?
-Because they represent, according to Jewish tradition, the two months of Adar in a leap year.
Picture is courtesy of Moshe Rimer.