Jewish Encyclopedia

The designer of the cover of the Jewish Encyclopedia used the Jewish Star here to create the formula: Star of David = Jewish. 
I took this photo at the Rockefeler Museum in Jerusalem , a very impressive background for such scholarly items.

Second Zionist Congress Delegate Card

Picture of  a lion inside the Jewish Star was copied from the Jewish Encyclopedia.
The following paragraph is from Dr. Asher Eder’s book The Star of David, which was published in 1987 in English in Jerusalem by Rubin Mass Ltd. The publication here is courtesy of Oren Mass
This version includes corrections and new materials that do not appear on the printed version

The famous Stadt-Kasino of Basel where the Congress took place had the six-pointed star above its entrance, and some meters away from it a white flag with two stripes, probably in dark blue.
The Delegirten-Karte (delegate's card) for the Second Zionist Congress in 1898, also in Basel, was decorated with a Magen David showing a lion in its middle field and seven five-pointed stars resembling the manner shown above (fig.19), embellished by two decorative stripes.
Meanwhile, the symbol had made its way to the United States. There, the American Jewish Publication Society adopted it as its emblem in 1873, while it was flown as a flag for the first time in 1904 at the St. Louis World Fair, in the design we know today.
The inventor of this flag may have been motivated, if not inspired, by the design of the Delegirten-Karte for the Second Zionist Congress.
Dr. D. Wolfsohn, a close friend and successor to Dr. Theodore Herzl, then suggested that the flag of Zion consist of the Star of David with the two parallel lines of the talith (the Jewish prayer shawl) above and below it. This suggestion might have been modeled on the aforementioned delegation card, and perhaps on the flag used in St. Louis (Missouri), although we have no proof of this.
Next, the Star of David graced the flag of the first Jewish army unit in modern history, the Mule Corps of World War I.
However, some decades passed until the 18th Zionist Congress approved this design as the flag of the Zionist Organisation and the Jewish people. The Congress, which took place in Prague in August 1933, put this sign out as a banner, thereby defying the slander which had become the official policy of Nazi Germany.

Star of David on Every Page

Magen David appears on each and every page of Theodore Herzl's newpaper, Die-Welt. All in all we talk about thousands of pages...What a great promotion for this symbol in its infancy.

The Promised Land Inside a Star of David

Magen David on the logo of Theodore Herzl's newpaper, Die-Welt, with a map of the promised land inside.

Die-Welt Cover

Prominent Jewish Star appears on the cover of Theodor Herzl's newpaper, Die-Welt, which was published weekly at Vienna since June 4, 1897.

Shulamit Gad

Many Magen Davids appear on the cover of Shulamit Gad's Hebrew book: King David and the Intensity of Psalms, which includes a whole chapter about the meaning of this national Jewish symbol.

A Star Shall Step Forth Out Of Jacob

Most researchers who are trying to solve the mystery of the origin of Magen David relate to the enigmatic verse in Numbers 24:17 "There shall come a Star out of Jacob, and a Sceptre shall rise out of Israel"` That’s why I thought it will be useful to collect a few sources which can shed light on this matter:

Shall step forth means rule, govern
Dr. Zvi Betzer says:
In Ugaritic the verb darakh appears in the sense of 'to rule, govern'.

Ayelet-Hashachar Hareuveni says :
the star is a shield in the shape of a star and the soldier stepped upon the part of the shield that was between two triangles and thus the shield had been stuck into the ground

Balaam is Laban the Aramean
Rabbi Shlomo Riskin says:
…the classic Targum (Aramaic interpretation) of Yonatan ben Uziel, identifies Balaam with none other than Laban the Aramean, uncle of Jacob-Israel

The star in the verse refer to King David

Maimonides:
I see him but not now ((Num. 24:17), this refers to David; I behold him but not nigh (ibid.) this refers to King Messiah; A star shall step forth out of Jacob (ibid.) this refers to King David; A star shall step forth out of Jacob (ibid.), this refers to David; and a scepter shall rise out of Israel (ibid.) this refers to King Messiah…

Uri Ofir:
The first time in the Bible that reveals any connection between the word "star", the word "David" and the words "nation of Israel" is in Bilam's speech. When Bilam sees the nation of Israel he says:
"There shall come a Star out of Jacob, and a Sceptre shall rise out of Israel" (Numbers 24:17). Rashi and Iben Ezra comment that Bilam's prediction is about King David. This is only a speculative connection that does not point on the shape of the Magen David (Star of David). The star in the verse refer to Bar Kochba
James Trimm says:
Bar Kosiba was renamed Bar Kochba (son of the star) and was declared the Messiah based on Num. 24:17.

The star in the verse refer to Jesus
Early Christians did believe Jesus was born under the Star because the prophecy of Balaam (Num. 24:17) said that the Messiah would be revealed by a regal Star.