
La Marchande de Poterie à Cologne dates from between August and October 1858.

La Marchande de Poterie à Cologne, Freer Gallery of Art
This is one of two studies for the etching La Marchande de Moutarde [20] which was printed by Auguste Delâtre (1822-1907) and published in the 'French Set', Douze Eaux-Fortes d'après Nature (Twelve Etchings from Nature) in 1858.
The drawing is fully catalogued in MacDonald 1995 (cat. rais.) [more] (cat. no. 272).

La Marchande de Poterie à Cologne, Freer Gallery of Art

La Marchande de Moutarde, National Gallery of Art, DC
Whistler's writing is not entirely clear. The word clearly starts 'Pot...', and could read 'Poterie', which is pottery. The drawing is difficult to interpret: the woman (who appears to have a stick or crook or umbrella under her arm) could be putting tops on bottles.
The Freer Gallery of Art website lists this drawing as 'Marchand de Potirons a cologne'. 1 Potirons are pumpkins, but there do not appear to be any pumpkins in the shop.
The city of Cologne in Germany.

La Marchande de Poterie à Cologne, Freer Gallery of Art

La Marchande de Moutarde, National Gallery of Art, DC
This is one of two studies for the etching La Marchande de Moutarde [20] which was published in the 'French Set', Douze Eaux-Fortes d'après Nature (Twelve Etchings from Nature). The etched image as printed appears in reverse.
The sheet was probably taken from a sketchbook. Over fifty drawings, many in sketchbooks, most of which dated from 1857-1858, were apparently given to Whistler's half-sister Deborah and/or her husband, Francis Seymour Haden, and were later removed from the sketchbooks.
See further details in r.: Les Côtes à Dieppe; v.: Cliffs and building m0222.
It was not, as far as is known, exhibited in Whistler's lifetime.
Due to the conditions of Freer's will, it cannot be lent to another venue.
1: Freer Gallery of Art website.