E KRUGER & Co, Paris.

39 Bvd de Strasbourg (1925), 9 rue St-Sebatien (1928), Marques EKC, CEKO, CORONA, AZUR. Azur has its own entry here under its original owner. Also issued cards with logo or at least series letters IMI on the face of the card but these cards carry the CEKO logo on the address side.

from ANNUAIRE DU COMMERCE DIDOT-BOTTIN 1921 PARIS - TOME II
from ANNUAIRE du COMMERCE DIDOT=BOTTIN 1925 Paris
This shows the older EKC logo on the front and the CEKO logo on the reverse
Showing the CEKO logo on the face of the card, 1920s radio.
An artist-drawn card
Corona Paris 7
Corona Paris 7 (verso)