Who can help me identify the stamps illustrated below? Again, I have no recollection of where they came from, but I think they may be North Korean, perhaps local, revenue stamps. I’d like to hear from anyone who can provide any insights into this stamp.
Note that it has many of the common perforation and centering errors that occur in DPRK early stamps. Figure 1 is a block of 4, centered very high and imperf vertically between. Figure 2 is a strip of four with triple vertical perforations between stamps 2 and 3, and 3 and 4. Figure 3 is a block of 4 plus with vertical perforations dividing the stamps in half.



(Originally from KP February 2007, Vol. 52, No. 1)
Postscriptum 2018
These stamps are not revenue stamps. The 우표 shows these are postal stamps, 조선 means effectively DPRK. The stamp shows the Kim Il Sung University building, as it was in 1949. The stamps were originally published in August 1949, but the stamps shown above seem to come from the reprinted version from 1957.
This is a scan of the listing of these stamps in the official Korea Stamp Corporation catalogue (2015):

The same stamps from the Scott catalogue. Notice one version is missing amongst the photos, but the reprint is listed:

According to Scott’s catalogue, 1955 to 1957, North Korea produced legal imitation “reprint” of its stamps from 1946 to 1956 to serve postal needs and to sale overseas. These reprints are imitations of the originals, but they are valid stamps.