The stamp marks the Arab Summit Conference held January 13-17,
1964, at which the Palestine Liberation Organization was founded to
carry out the goal of eliminating Israel. The error on the map is not
the omission of Israel. That is not an error but propaganda. The error
is that the map does not show the Gulf of Aqabah or the Red Sea, but
rather a land mass south of Israel or Palestine. And further, the
southeastern border of Jordan (shaded in pink) with Saudi Arabia does
not reflect the current border.
Jordan and Saudi Arabia agreed to some boundary
exchanges in 1965. I have not been able to find any details of these
exchanges, but they may account for the difference in borders between
the stamp, and current maps.