The Crown image of the Merkavah is as relevant as the Throne and Chariot. They are interchangeable. It relates directly to the Great Angel Measurement, the wearer of the Crown, who defines the outer limits of the Sanctuary.
Excerpts from Keter: The Crown of G-D in early Jewish Mysticism
Copyright of Princeton University Press
Notes are my interpretation.
The most pragmatic of all references to divine Kingship in the regular weekly liturgy is in the introduction to the "Qedushah"... as recited by Sephardic Jews in the "Mussaf" service on Sabbaths, New Moons and Festivals.
"A Crown they give unto you, YHWH our G-D, angels enthroned above and your people Israel gathered below. All of them thrice proclaim your holiness, as has been spoken by the prophet's word: "They call out to one another, saying: "Holy, Holy, Holy is the Lord of Hosts! The whole earth is filled with His Glory!"
In the liturgy Israel recounts an enthronement rite that takes place daily in the upper realms. But in the "Qudushah" of the Amidah repetition, which requires a quorum of ten for public recitation, Israel rises to join in with the angels in bestowing the crown upon the divine head, the joint gift to G-D from His loyal legions above and below. "Dwellers in the upper and lower realms."
Sandalphon, Metatron, Keruviel and Serafiel
It is taught in the Mishnah that Sandalphon.... is taller than his companions by 500 years (measures)... stands behind the Merkavah and binds (Qosher) crowns....
Great many sources speak of a name of G-D or another phrase "engraved" or "inscribed" on the crown. Sometimes it seems that the crown itself is altogether made up entirely of words.
Said Rabbi Ishmael: "I saw the cosmic King seated on the High and Exalted Throne, [accompanied by] a single troop that stood [reaching] from Earth to Heaven. Its name is Sandalphon. At the time that he seeks -Rozey YHWH the G-D of Israel, to swear by the "Tefillin" and to cast an oath by his hand, he takes the "Tefillin" from his head and he nullifies decrees from the earth."
Perhaps G-D is swearing to cancel a previously issued decree that caused some plague or other destructive force to be unleashed against the earth's inhabitants...
Frequently understood in the Merkavah sources, is that the Righteous Human Practitioner, armed with the knowledge of the upper worlds, can administer an oath "Mash Bi'A" (the causative of "Sh-B-", the root for "oath making"), or "adjure", the heavenly forces to avert such decrees.
It is noteworthy that the phrase "Mevatiel Gezerot" is reminiscent of another Talmudic statement, one claiming that "the Blessed Holy One issues a decree, but the Righteous one nullifies it.
"The richest source for coronation descriptions is "Sefer Hekhalot" and 3 Enoch."
He is the interpreter (meturgenian) between Israel and their Father in Heaven, as the scripture says; and there was a single wheel on the ground next to the creatures. "His name is Sandalphon and he binds crowns for the master of the Glory (ba'al ha-havod) out of the "Holy", "Blessed is He", and "Amen, may His name be blessed" which Israel offer as responses in the synagogue. He adjures the crown by the explicit name and it ascends to the Lord's Head. (Rosh Ha-Ad On)
For this reason the sages say that anyone who misses a "holy", "blessed be He" or "amen" may his great name be blessed", causes the crown to be diminished and is liable ... until he repents and brings sacrifice before the righteous in the future to come.
Note: The size of Sandolphon's head is the same size and is of the same space as the wheel of the Chariot/Crown. i.e. The crown fits the wearer.
The Coronation of Metatron
The blessed Holy One fashioned for me a majestic robe, in which all kinds of illuminaries were set, and he clothed Me in it. He fashioned for me a Kingly crown in which 49 refulgent stones were placed, and like the sun's orb, and its brilliance shone into the 4 quarters of the heaven of 'Averot, into the 7 heavens, and into the 4 quarters of the world. he set it upon my head and called me "The lesser YHWH" in the presence of the whole Household in the height, as it is written, "My name is in Him." (Ex 23:21) (3 Enoch 12)
Note: 49 relates to the 49 solar years between Jubilees.
After Metatron tells the heavenly Voyager (and narrator) of "Sefer hekhalot" the tale of his own ascent, he takes his visitor on a tour through the heavens. As they go through the upper realms, the voyager is soon shown a being called Keruviel, who, as the name indicates, is the head of the cherubim in heaven.
Above them is a prince, Noble, Wonderful, Mighty, praised with all manner of praise: Keruviel YHWH is his name, a valiant prince, full of boundless power, a majestic prince, with whom is majesty: a righteous prince, with whom is righteousness; a Holy prince, with whom is holiness; a prince glorified by thousands of hosts, a prince extolled by countless legions.
A crown of holiness in upon his head, with the sacred name engraved upon it, from which lightening flickers.
The bow of the Shekinah is across his shoulders. His sword, like a lightening flash, is on his thigh, his arrows, like lightning flashes, are in his belt, his breastplate of consuming fire hangs around his neck, and coals of Juniper encompass him. The splendour of the shekinah is on his face; His Horns of majesty are on his wheels, a royal turban crowns his head.
The crown on his head is radiant like the Throne of Glory, and the height of the crown is a journey of 502 years.(measures) There is no other kind of radiance, no other kind of splendour, no other kind of brilliance, no other kind of light in the world that is not placed in that crown.
Serefiel is the name of that prince, and the name on his head is "Prince of Peace."
Note: I consider these 4 angelic names to be of the same angelomophic size as they all wear the crown, in contrast to those who carry the Throne, of which the crown is made up. The 4 directions of the Crown can allow for 4 names.
The Throne and the Crown
... like the king who had a Throne. Sometimes he carried it in his arm and sometimes on his head.
(The students) asked (the master): "Why?"
He replied: "because it was beautiful and he was hesitant to sit on it."
They asked: "And where did he put it?"
He replied: "On his head.... " (Bahir 25)
You said "His Throne?" But we have said that this is the crown (Keter) of the Blessed Holy one.
Thus we have said, "With 3 crowns are Israel crowned: The priestly Crown, the Royal crown is above it but the Crown of Torah is above them both."
Note: The Priestly Crown is largest, the 1st in plan, 2nd in elevation. The Royal Crown is 2nd in plan, 1st in elevation and the Torah tiara is 3rd in plan and 3rd in elevation. The tiara is most holy as it is closest to and encircles the Throne Room.
It is the geometric essence of the other crowns.
To what can this be compared? To the king who has a fragrant vessel that he loved greatly. Sometimes he lends it to his son to sit with him. Sometimes it is called his throne, because in his arm he carries it like an amulet, a kind of cup. (Bahir 101)
Israel is the Crown of G-D, but they seem here also to be his Throne ... G-D "is enthroned in the praises of Israel." (Ps 22:4)
He dwelt in the tabernacle they made for him, seated upon the cherubim. In fact the tabernacle itself is once depicted as G-D's crown ...
The Crown of David
Hekhalot Rabbati: (After showing me the tribulations that await Israel, Hadariel) brought me into the treasures of the consolation and salvation. There I saw bands of ministering angels sitting and weaving garments of salvation making crowns of Life ('Osim Kitrey Hayyim), setting precious stones and pearls into them. (They were also) mixing all kinds of perfumes and sweetened wines for the righteous.
(Footnote: Wines to be drunk at the Messianic Banquet: Barakhot 346. and Gilisberg legends, vol. 5.)
I saw one crown different from all the others; it had a sun, moon, and 12 constellations fixed on it.
I said to him: "O Glorious Heavenly light! For whom are these crowns?"
He said to me, "For Israel."
"And for whom is this special crown?"
He said to me, "For David, King of Israel."
I said to him: "O Glorious Heavenly light, show me David's' Glory!"
He said: “Wait here, my beloved, until David arrives, and you will see his greatness. "He took hold of me and seated me in his bosom. He said to me, "What do you see?"
I said; “I see 7 bolts of lightning running about as one."
He said: "Hide your eyes, my son, that you not be shaken by these, which have come forth to greet David."
Immediately there came forth all the Ofanim, Seraphim, "Hahot", the treasures of hail and snow, the clouds of glory, the stars and constellations, the ministering angels and fiery beings of Zebul, saying: "For the conductor, a Psalm of David. The heavens declare the Glory of G-D." (Ps 19:1-2)
I heard the sound of a great noise coming from Eden, saying, "May YHWH Rule forever!"
I saw David, King of Israel, at their head and all the Kings of the House of David following him.
Each of them had his crown on their head, but the Crown of David was more brilliant and glorious than all of the others, its radiance extending from one end of the world to the other...
Once David had entered the Great House of Study, (Bet Ha- Midrash Ha-Gadol) in the firmament, a fiery throne was awaiting him, 40 parasangs high and double that in width and length.
Note: 40 measurements high and double that in length.
When David came and was seated on the Throne prepared for him, facing the Throne of his master, with all the kings of Israel standing before him, David immediately began to recite hymns and praises like no ear had ever heard.
Once he opened with: "May YHWH Rule Forever", Metatron and his entire retinue began to say: "Holy, Holy, Holy is YHWH SEVA'AT."
The "Hayyot" recited praise and said, "Blessed is the Glory of YHWH from His place."
The firmaments said, "May YHWH rule forever."
The earth said, "YHWH is King, YHWH was King, YHWH shall be King forever."
And all the Kings of the House of David said: "YHWH shall be King over all the earth; on that day will YHWH be one and his name one."
Note: David's crown is the political aspect of the Merkavah's 3 crowns. It contains the court of 70 Kings as presenters of earthly issues to the Merkavah. It is the lowest position, and second in width. David here, is the Political Messiah presenting the earth to the Angels.