It is perf 11. I also noticed a slight crease that I never noticed before. Yes it is without tab.
At first Israel stamps were collected without tabs and if it had a tab all well and good. Then the tab frenzy took off. I seem to remember Scott valued a used stamp at a few hundred dollars in the 1960's.
Remember, in 1948/1949 50 cents was relatively a lot of money. It well may have been the equivalent of the $10-$20 you expected. In fact 50 cents was my whole allowance for the week. I had enough money to go to the movies on Saturday afternoon and enough left over to get snacks during the week. When the allowance went to a dollar I was rich.
When this stamp was bought Israel had recently become a state and the only stamps in abundance were Palestine. As I was told, there were no Israel stamps on the US market, unless they came on mail to family members. I believe Jacques Minkus became the largest US dealer for Israel stamps. Now there are a few dealers. I will say Israel stamps became desirable and pricey pretty quickly, especially in New York City.
Quote: Remember, in 1948/1949 50 cents was relatively a lot of money
My feeling is that you purchased your stamp before the real value was known. Even in the late forties, it should have been more than 50c. But a small crease may have had something to do with it. Still, it has a personal historical fascination and that makes it a treasure. It is also a very beautiful stamp...indeed, the whole set is lovely.