Suveiniškis (by ca. 1930 Suvainiškiai, then Suvainiškis) is a township in north-eastern Lithuania, ca. 45 km north-west of Rokiškis. In World War One it was passed through by 78. Reserve-Division on ca. September 11, 1915 while moving on Daugavpils (Dvinsk, Dünaburg). During the war Suveiniškis was linked by rail with Skapiškis.
During the German withdrawal from Russia in late 1918, this area came under Soviet control in late December but was reclaimed by a unit of Lithuanian regulars, led by Jonas Variakojis Sr., on June 7-9, 1919.
Suveiniškis had no postal facility during the czarist period. A Lithuanian post office, possibly an agentūra, was set up in 1921 but so far no further details are available about its origins and staff.
For stamps, Suveiniškis appears to have had a stock current in 1921-1922 etc. In the absence of a postmarker, cancelling at Suveiniškis at first may have been done in handwriting, but as yet no such items have been noted. By 1922, cancelling was done by means of a regular double-framed boxed cachet inscribed “SUVEINIŠKIS”.
A standard calendar-type postmarker was provided in ca. 1923 also inscribed “SUVEINIŠKIS”. By 1930, subsequent postmarkers carried “SUVAINIŠKIAI”. However, the township is also known as SUVAINIŠKIS.
Known provisional markings:
Cancelling by boxed cachet:
5 / IX  single, 4a/75 [colln. Doniela]