This appears to be a study or preliminary sketch of his painting, "Yellow-Red-Blue" on heavy paper. This mixed media item measures approximately 12 1/4 × 7 5/8 inches.
I purchased this item from a private owner some years ago but I don't recall if it was at an estate sale, liquidation sale or other. This item is pencil signed "CK" on the upper left corner of the item and pencil signed on the reverse. There also appears to be a stamp of some sort on the reverse but it is faint, especially against the black painted background
Thank you for submitting your item for appraisal. There is no way to put it mildly - this is just a blunt fake of recent production, inspired by on of Kandisky´s paintings. The backside is covered with black ink to conceal something or avoid examination of the painter. The stamp " Hermann Mayer ..." is just a red herring of no importance. If you happen to not agree with my opinion you could have the watercolour provenance checked ( it would have appeared in an auction in the last 100 years), you could check the pigments etc. I would advise you to save money and try your luck with another painting or ask before buying. There is no measurement for the sentimental value you might attach to the item.