Focus on this artwork and analyze the Physical history.
The tondo dates to Michelangelo's time in Florence before his move to Rome in 1505. According to the art historian, Vasari, while working on his David, Michelangelo "also at this time... blocked out but did not finish two marble tondi, one for Taddeo Taddei, today in his house, and for Bartolomeo Pitti he began another... which works were considered outstanding and marvellous".To the lower right of the back of the relief is a ligature combining the letters L and A, probably the mark of another carver or dealer, considered most likely to be the initials of Lapo d'Antonio di Lapo, active at the Opera del Duomo and for a short period in 1506-1507, one of Michelangelo's assistants. A chisel blow on the reverse seemingly from this earlier phase resulted in a hairline crack in the face of the Virgin that may only have become apparent as carving progressed. In consideration of his motivation to continue working on the damaged marble after that was obvious, speculation exists about whether Michelangelo, known for his concern for his materials, was constrained by a shortage of ready alternatives, or, considering his success with the damaged block for David, was more accepting of flaws because he was confident in his ability to work around them.  The missing segment to the bottom right may be a result of an excess of his celebrated "direct attack".  At some point, however, work on the tondo ceased. Five holes in the outer rim of the tondo were intended for fixings and are variously dated.Although unfinished, the tondo appeared in the Palazzo Taddei and is documented as still there in 1568, but by 1678, the family had moved to a new residence near San Remigio. At an unknown date the tondo was taken to Rome, where it was acquired from Jean-Baptiste Wicar by Sir George Beaumont in 1822. Initially hung at Beaumont's house in Grosvenor Square, it was bequeathed to the academy in 1830 and installed at Somerset House, before moving with the academy to the east wing of the new National Gallery building in 1836, where it remained until the academy relocated to Burlington House in 1868. Except for an exhibition at the Victoria and Albert Museum in 1960, the tondo has been housed and displayed in various academy locations ever since. 
The discovery of the hairline crack running through the upper half of the marble contributed to the decision in 1989 to provide a permanent home for the tondo. Subsequently the tondo was cleaned with dichloromethane swabs and clay poultices to remove residues of nineteenth-century plaster casts and their oil-based release agents, packing materials, traces of beeswax and pine resin adhesives, and other surface accretions. The tondo was left unwaxed and no other coating was applied, as the work is not "finished" and originally had not been polished (as was the David when finished). Since the opening of the Sackler Wing of Galleries in 1991, the tondo has been on free public display in an area designed for it on the top floor that was positioned for reasons of preventive conservation behind protective glass, to combat the effects of air pollution and the possibility of vandalism.
Grosvenor Square new National Gallery building Sir George Beaumont cleaned Burlington House Rome dichloromethane National Gallery air pollution San Remigio Florence poultice marble his move preventive conservation pine resin another Jean-Baptiste Wicar Pitti Somerset House Michelangelo's time relief tondo David Opera del Duomo ligature vandalism Michelangelo plaster casts release agent beeswax Victoria and Albert Museum Vasari