East Karelia 1,75 mk grey, overp black, block of 4 Karhumäki 20.IX.42

(The cancellation may slightly differ from image)
Overprinted in black 'Itä-Karjala Sot.hallinto'.
The overprint translates, 'East Karelia Military Administration.'
The coat of arms Finland model m30.

Block of four with different types of this stamp:
3x IK 1 I Overprint 'Karjala': middle letter A tip is flat.
1x IK 1 II Overprint 'Karjala': middle letter A tip is sharp.