As told in the thread GERMAN FIELDPOST :

KURLAND

The so-called Kurland express letter
Halved registration number 4 used as an approval mark for airmail in Courland.
Two armies, the 16th and the 18th, had been included in Kurland since October 10, 1944. From mid-March to the end of April, the Kurland Schnellbrief was used to quickly establish a field post connection to the homeland for the wounded and later for everyone.
The stamps were halved with a paper cutter. Often the perforation was not cut in the middle, so that vertically unserrated halves occur due to the manufacturing process.
The halved stamps were stuck on cards and letters (field post forms) to protect against counterfeiting and were stamped with the service stamps of the field post control center 734 (half) Libau (lq and 17092).
Counterfeits to the detriment of the military post have occurred. The number of "Kurland Schnellbriefe" received and actually flown is low and comes almost exclusively from the period from mid-March to late April, addressed to areas of Germany not yet occupied by the Allies.
Empty cards and letters with the stamp DDPO Libau "c" were still "manufactured"

Well now I have one, but a little cut-off on the right side (Signed by Alberto Diena) :