The time is coming when letter writing with pen and ink and sent as a personal message from one person to another will be as much of a rarity as the gold pocket watch carried on a chain —Andy Rooney
(pasted from: The free dictionary)
Two sisters, one at home and the other one service maid in France and Belgium, exchanged cards whose only aim was to keep in touch.
Back and front of the cards, reproduced by gum bichromate photography.
For more information on the photographic process see:
St Pauls Photography – Gum Bichromate (youtube video)
Caution: be aware that potassium and ammonium di/bichromats are strong oxidising agents, thermodynamically unstable with strong combustion reactions; like all chromium VI compounds they are highly toxic and cancerogenic.
originals by N. Schumacher, Mondorf les Bains and Verlag von S. Meyer-Schock, Buchdruckerei, Grevenmacher