Aknīste is the present Latvian name for the tsaristic ЭЛЛЕРНЪ (EHLLERN), a transcription of the German name Ellern.
On Wikipedia is a list of German names of Latvian places: according this list the German Ellern is Elkšņi. This has been also a Latvian indication for this place and there are more: Akniši, Okniste.
Aknīste is located in southern Latvia, near the Lithuanian border.
Aknīste formed part of the Polish-Lithuanian area and after the war of independence is was Lithuanian. In the early 1920s Lithuania exchanged Aknīste for Palanga.
It is a one-ring postmark and in the postmark we see the Russian indication ЭЛЛЕРНЪ (EHLLERN) and КУРЛ Г. (KURL G.), short for КУРЛЯНДСКАЯ (KURLYANDSKAYA) ГУБЕРНIЯ (GUBERNIYA), Courland Government.
It is a ‘crossed-date’-postmark: type 6 with month in numerals is type 6C (with gubernia) and 6D (without gubernia), the ‘cross-date’-types. So here type 6C.
Here we see the indication ПОЧТ. ТЕЛ. ОТД, the abbrevation for ПОЧТОВО-ТЕЛЕГРАФНОЕ ОТДЬЛЕНIЕ (POCHTOVO-TELEGRAFNOE OTDELENIE = Post-Telegraph Sub- Office), so according the EESTI-classification this is type 6C2.