A variety of labels used by Alfred Flechtheim and his galleries for inventories of his holdings are known and have survived to this day on the backs of pictures. However, provenance researchers have not yet managed to decipher definitively either the system used or the combination of numbers on the labels.

What is certain is that the light-coloured label in portrait format was used after the opening of the gallery in Berlin in October 1921. It bears the heading ‘Galerien Flechtheim’ in capital letters with ‘BERLIN W 10’ left-justified further down and ‘Lützowufer 13’ below that, ‘DÜSSELDORF’ right-justified further down with ‘Königsallee 34’ below. Below the addresses and a thick line across the label there are six well-spaced dotted lines, the first three of which have, from the top downwards, a ‘B’, ‘D’ and’E’ at the beginning, respectively, in capital letters. In these lines, the letters were allocated to combinations of up to five numbers; sometimes additional letters and various sequences of numbers. In addition, these adhesive labels generally have the name of the artist and sometimes other details added by hand in the lower third, e.g. a circled single digit in a different colour and the title of the work and/or date, mostly in ink. It is very probable that the abbreviation ‘B’ stands for Berlin, ‘D’ for Düsseldorf and ‘E’ for Eigentum (private property). Special marks for one’s own property was more than usual for a variety of reasons.

There are also some smaller, rectangular, light-coloured, landscape-format labels with the printed heading ‘Galerie Flechtheim’, below which is a very broad line across the whole width of the label with ‘Nr.’ (no.) below that in the middle with the handwritten addition of, for example, 4-digit combinations, sometimes supplements with handwritten notes (perhaps added later), in the form of one or more combinations of letter and numbers, for instance. The likely presumption is that the labels refer to the time when the Düsseldorf gallery was the only one, i.e. 1921 and earlier; additions, e.g. B. 2222 [fictive example] could point to the transfer of the works to the Berlin gallery.

Small, light-coloured labels with Flechtheim’s printed initials, designed by Richard Schwarzkopf, were used after the opening of the gallery in Düsseldorf in 1913. This trademark also applied to catalogues, issues of ‘Der Querschnitt’ during the first few years and also, in 1931/31, for ‘Omnibus’. Apart from the initials, labels may have a stamped captital letter such as a bold, darkly printed ‘F’, to the right of which a row of up to 4 numbers was added by hand. Whether ‘F’ stood for Frankfurt or Flechtheim is still open to conjecture.

A rectangular label in landscape format on bright-red paper is also known. At the top, above a thick line across the label is ‘Galerie Flechtheim’ in capitals with ‘No. 222’ [fictive example] – a 3-digit number added by hand – below the line in the middle. The description and the height of the numbers could be connected to a previous use when the first gallery in Düsseldorf was operating. 

The ‘K’ question: Many, albeit more recent labels have the letter ‘K’ on them together with a combination of numbers. The abbreviation could stand for ‘Kommission’ (commission), Kahnweiler (Galerie Simon), Köln (Cologne) or ‘Kauf’ (purchase). Often the meaning actually becomes apparent from the provenance of the picture, i.e. it is evident that it is a work on a ‘sale or commission’ basis from Kahnweiler, and marked accordingly. In such cases  Flechtheim took over Kahnweiler’s numbering system.

Whether number combinations need to be deciphered or whether they were even codes is, at present, something still open to speculation. Basically, numbers were used to list the works of art in ascending order. They could, as already mentioned, by encoded number combinations that record the year (19)28 or a sum 30(00), for example.