The design of the silver ring base was originally conceived as part of the 'flaches Modell' series of cutlery, 1903/4.
A contemporary photograph from the MAK WW archives shows the silver ring, presumably a napkin ring, in a tray with examples of each of the cutlery items. (See Waltraud Neuwirth, Josef Hoffmann. Bestecke für die Wiener Werkstätte, Vienna, 1982, p. 29, fig. 12.)
The actual design for the salt with glass liner appears as No. S156 in the MAK WW archives (reproduced ibid, p. 40). The archives record that only eight examples of this model were made in silver.
The design was included in one of over sixty table setting displays devised by Moser and Hoffmann for the Wiener Werkstätte's 'Der gedeckte Tisch' ('The Laid Table') exhibition in 1906.
cf. Viennese Silver. Modern Design 1780 - 1918, Michael Huey, ed., Neue Galerie exhibition catalogue, New York, October 17, 2003 - February 16, 2004, p. 216, the relevant table setting (reproduced from Deutsche Kunst und Dekoration, Vol. 19, 1906/7, p. 471) illustrated.