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Cathedral of Saint Mary, Gdansk, Poland. Black Madonna, Horns of Mithra?
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The Black Madonna at the Church of Saint Mary, Gdansk, is haunting because of its ambiguities. There are elements, symbols, of several religious traditions. All of this is not necessarily Christian in the traditional sense. This could be Mary, as in Maria Regina, see monogram-like design at right of the portrait here.  Then there is a six-pointed star, with a crown-outline above? Judaism? Other forms here?

1.  Early Christianity was a blend of multiple ideas, interpretations, and other systems, inlcuding ideas from the gnostics, and even adherents of the Mithraism that Rome fostered. Paul was raised in a town known for Mithraism.  See http://www.tertullian.org/rpearse/mithras/display.php?page=mithras_and_christianity These links, influences, are not new.  Each school of thought had strong groups of followers, until the Roman Catholic Church took it upon itself to be the Decider, the sole arbiter of correct institutional dogma, and killed, excluded, held Inquisitions, Crusades, etc. against those of differing views.
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2.  With that background of cultural exclusionism, ask what is the origin of this particular Black Madonna. 

Is it Sara La Kali?   

There is a tradition in the Gypsy, or Roma, community, for "Sara La Kali" - the handmaid to Mary when Mary landed in southern France.  She became the Roma patron saint.  Look at the symbolism. I explored the issue at this site, see http://bogomilia.blogspot.com/2007/12/sara-black-or-sara-la-kali-roma-saint.html/  There is a long tradition of Roma culture in Poland, see report at http://www.romowie.com/the_report.pdf

Another version of that story provides that Sara, of dark skin, living in a community of Roma metalworkers on the Rhone River, rescues a sinking boat by casting out her cloak, and on the boat are the traditional Three Marys who are all saved thereby.

• The Three Marys:  Mary the mother of Jesus, Mary the mother of James, and Mary Salome, see http://www.radoc.net/radoc.php?doc=art_b_history_romanireligion&lang=en&articles=true.  Mary Salome:  Also known as Salome, the midwife who, according to the Gospel of James later excluded from the canon, aided in the birth of Jesus and was the beneficiary of the first miracle, a healing of her withered hand.  See http://www.gnosis.org/library/gosjames.htm; and http://martinlutherstove.blogspot.com/2008/11/james-just-unjustly-usurped-secret.html

Some merge Sara's stories with Salome's.

3.  This painting in Gdansk:  There are some reasons to conclude so far that this is not Mary mother of Jesus.
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No babe is to be found with the Madonna. The appearance is not like a traditional Madonna, particularly in costume and skin tone.  The horns and other symbolism suggest another identity, as does the skin tone.
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3.  Assistance needed:

Can anyone translate the information: Madi Staza Nami at the bottom? Then at the top, Matro Mieusie Ruzia .  - looks like mother Russia? Is the face black, as Sara la Kali's is traditionally represented, or is it silver that has tarnished?
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But most places polish the old silver. Why would this blacken?
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3.  Is it possibly modern? See the sunburst theme around holy heads.
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4.  The arc has long been a symbol of the moon, receptivity, even the Holy Grail, see http://symboldictionary.net/?p=1914 .
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5.  Mithraism:  The bull featured in this pre-Christian religion.  This was the official religion of Rome before becoming Christian in about 300-400 CE.  See the similarities between the two at Mithra and Christianity, at http://mithra2004.tripod.com./Mithra%20and%20Christianity.htm  Symbolisms and life events overlap. See http://mithra2004.tripod.com/Cult%20of%20Mithra.htm
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Meitros is another name for Mithraism, see http://www.cais-soas.com/CAIS/Religions/iranian/Mithraism/mithraism_and_christianity.htm
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St. Mary's is the largest medieval brick church in Europe, 1343.  It was constructed over 150 years.