Kiev 4/4a without logo on the clip (1968)

Several strange 1968 Kiev 4 and 4a appeared recently on the net: they don't wear the usual logo, nor "made in USSR" on the accessory clip, only the serial number. There is nothing else different compared to the running production.

For the moment, we don't know why. Several hypothesis are evoked in the related thread here: https://ussrphoto.com/Forum/topic.asp?TOPIC_ID=3693

Known serial numbers:

Type------Serial number-------Lens s/n--------------Owner/origin

4a_______6806307___________Jup 8M 6821801_____seen on the net

4a_______6808112___________Jup 8M 6825050_____seen on the net

4a_______6808417___________Jup 8M 6823873_____Jacques M.

4a_______6811264_____________________________Alexander K.

4________6816062_____________________________"1200 cameras..."

4________6816332___________Jup 8M 6824327_____Jacques M.

4________6816711___________Jup 12 7804048_____French collector

4________6817037_____________________________Alexander K.

4________6819315___________Jup 8M 7727255_____seen on the net