Hungarian KÖV

Hi, I need some help from you experts!
I have a couple of letter to Hungary and one to Bulgaria with the imprint in black of a postmark with the text KÖV., I believe it is a Hungarian passed through postmark, or? but what is the meaning of the abbreviation KÖV. ?
I'm greatful for all help, I need it!
Regards
Kjell Nilson, Sweden
I have a couple of letter to Hungary and one to Bulgaria with the imprint in black of a postmark with the text KÖV., I believe it is a Hungarian passed through postmark, or? but what is the meaning of the abbreviation KÖV. ?
I'm greatful for all help, I need it!
Regards
Kjell Nilson, Sweden