Freemasons and their art are along the lines of the FlatEarthers.

NASA Freemasons created globe earth CGIS' and passed them off as pictures; You fell for the deception. :-[

The arch above denotes the Firmament, and it is divided into the four quarters, to denote the 4 cardinal directions. The line about the midsection denotes the flat plane of earth. The cross above means Christ has dominion over all.
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Yes, yes, I know you need a globe to prove the world is flat.  

That is a representation of the firmament above and the firmament below.

That is a representation of the firmament above and the firmament below.

Being that this object dates back many hundreds of years, and is included in Catholic visions, art, publication, etc...Could you link a quote that describes it representing the firmament?
If you look at the history of it, its just the Catholic adaptation of an old pagan symbology 

https://en.wikipedia.org/wiki/Globus_cruciger

"Holding the world in one's hand, or more ominously, under one's foot, has been used as a symbol since antiquity. To citizens of the Roman Empire, the plain round globe held by Jupiter represented the world, or the universe, as the dominion held by the emperor. A 2nd-century coin from the reign of Emperor Hadrian shows the Roman goddess Salus with her foot upon a globus, and a 4th-century coin from the reign of Emperor Constantine I shows him with a globus in hand. The orbis terrarum was central to the iconography of the Tetrarchy, representing the Tetrarchs' restoration of security to the Roman world. Constantine I claimed to have had a vision of a cross above the sun, with the words "In this sign, you shall conquer" (Latin: In hoc signo vinces), at the Battle of Milvian Bridge in 312. His soldiers painted crosses upon their shields, and then defeated their foe, Maxentius.
With the growth of Christianity in the 5th century, the orb (in Latin scriptures orbis terrarum, the 'world of the lands', hence the word "orb") was topped with a cross (hence globus cruciger), symbolising the Christian God's dominion over the world. The emperor held the world in his hand, to show that he ruled it on God's behalf. To non-Christians already familiar with the pagan globe, the surmounting of a cross sent a message about the triumph of Christianity.^{[citation needed]} 

Our Lady of the Miraculous Medal, 
Pray for us.  

has been used as a symbol since antiquity. To citizens of the Roman Empire, the plain round globe held by Jupiter represented the world, or the universe, 

Yes, because all the peoples of all ancient cultures, pagans AND Jews, understood the entirety of Creation (the world, the universe) to be designed this way.
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https://10sciencereligion.weebly.com/hebrew-no-1.html

Yes, because all the peoples of all ancient cultures, pagans AND Jews, understood the entirety of Creation (the world, the universe) to be designed this way.
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https://10sciencereligion.weebly.com/hebrew-no-1.html

Not another cartoon, well at least this is different from that other pagan art they worship.
We Catholics will hear the words of the Virgin Mary when she designed her medal.  I am sure she knows the shape of the earth since she is the Queen of the universe.  BTW ... she said GLOBE. In fact, she held the globe in her hands so there will not be any mistake from the Pagan theory.