Posthume signature

In 2001 Sotheby's Amsterdam had 16 paintings and drawings of Zandleven in its auction, all being from the estate of Miss Daendels. Not sold was a.o. JAZ-1909-053:

JAZ-1909-053
Damaged sun flowers in a vase

Black chalk with heightened white, 40 x 30 cm
Not signed, 1909
Owner unknown
AUCTIONS
   Sotheby 2001(AM0812) cat. nr. 1161
   Notaris Arnhem 2003(jun) cat. nr. 28
   Venduehuis 2003(okt) cat. nr. 0458
NOTES

a bit crayon, on grey paper, estimated about 1909

PROVENANCE
   Private owner

In june 2003 the Notarishuis te Arnhem had in its auction: Withered sunflowers, Drawing, 38,5 x 29 cm, Signed, 1907. Since the catalogue mentioned "signed, 1907", we didn't recognize it and added it to the collection as 'newly found'.
But, on October 3, the catalogue of the Venduehuis der Notarissen te 's Gravenhage mentioned in its catalogue, number 458: Sunflowers, signed bottom left, 1907 chalk-drawing, 38,5x29 cm. A photograph was added:

So, recently someone signed the drawing on behalf of Zandleven, probably to improve its sellability. The year 1907 doesn't look bad, the drawing was estimated by a connaisseur as made in 1909.