To call it a painting is to flatter it. It is a framed off-white canvas decorated with a lattice of strips of coloured adhesive tape. Towards the bottom of the painting, as hung, the strips gets closer together. According to the expert curator those strips should be at the top.
The simplest way to determine whether she's right would be to ask the artist but sadly Piet Mondrian, the Dutchman who stuck the tape on to the canvas, has been dead since 1944.
The curator, however, has evinced evidence in the form of an almost identical Mondrian painting with an almost identical title on display in a museum in Paris. It has the closer-together lines of tape at the top.
But who is to say that Paris has it right and Dusseldorf wrong? Why could it not be the other way around?
The curator further points to a photograph of the artist's studio in 1941 which shows the painting on an easel, again with the closer-together tapes at the top.
But that is no clincher either. When applying adhesive tape to canvas there is such a thing as a convenient height to work at, even for a genius like Mondrian.
I see no reason he should not have turned the canvas upside down so as to work on its lower parts without having to bend.
According to the critic Robert Hughes, Mondrian was 'one of the greatest artists of the 20th century' and 'one of the last painters who believed that the conditions of human life could be changed by making pictures'. I cannot tell you what Hughes meant by this.
What I can tell you, however, from close study of Mondrian's Wikipedia entry, is that as a youngish man Mondrian painted some pretty enough things in the manner of the Impressionists or his compatriot van Gogh.
But from about 1920 he produced only abstract works, consisting of blocks of primary colour marked off by horizontal and vertical lines.
These paintings made him famous and since his death they've become hugely valuable. In 2015 a painting Composition No III, with Red, Blue, Yellow and Black sold for $50 million. I cannot tell you why. I just hope it came with a discreet little sticker showing which way up to hang it.
The Dusseldorf painting is called New York City 1, and its sister painting is in Paris New York City. (A cynic might suggest that the existence of two effectively identical paintings with effectively identical titles smacks of an excess of commercial greed and a shortage of artistic inspiration, but I am not qualified to comment.)
What the titles do suggest, however, is that these are not entirely abstract works and that they are intended to represent New York in some way.
The expert curator seems to agree. She says the closer-together strips clearly represent a darkening sky above the city and should therefore be at the top.
But one could just as well argue that they represent a streetscape, or a road surface, and should therefore be at the bottom.
Even more plausibly perhaps, the canvas could be turned through 90 degrees in either direction whereupon the closer-together strips could represent that universally recognised symbol of New York, a skyscraper.
There is however a further alternative, which is to say who bloody cares and turn with relief from Mondrian to the greatest paintings of all time bar none, the still lifes by the Dutch old masters of the 15th, 16th and 17th centuries, paintings of pheasants, pewter, pomegranates and who knows what else, all of them done with a skill and delicacy and truth to life that make one gasp, and not one of which has ever been hung upside down or ever will be.