Which one is earlier? I think they just replaced "J" with "I" later, since Chajka seems like a Polish or Czech phonetic transliteration to English and not Russian... correct Russian would probably be with "I".
Allain is right! Those cameras were once faily common in Brazil including the rarer grey model! They competed with Olympus Pen ! Interesting to say that those cameras were brought to Brazil in 1965 to 1968 and they come with an empty cassete that was different (shorter) from commercial cassetes that comes loaded with film, - Result- They did not accept standard film. All those cameras were so re-machined to fit stardard film on chamber, and repainted internally. I took on the organizing remanufacture of those cameras. Regards LP