The question is what does CK mean at the end of an SKU, if the listings are correct?
See
https://sourceit.com.sg/search?type=product&q=Kobo
I searched generally and even the IR touch Aura H2O ends in EP, but the two Elipsa models end in BU. The Sage and Libra 2 end in EP.
e.g. SKU N250-KU-BK-K-EP Kobo Aura H20 Black
Always starts with N and three digits*, optional letter, and -KU-
Colour code of two letters, BK = Black, WH = White, OB = Deep Ocean Blue.
-K-
Two letter code at the end: Most are EP, the two Elipsa models end BU
Does CK mean colour screen or something else?
[* There seems no rhyme or reason to the three digits.]