Another Grunau Baby IIb kit announced this time by Kovozávody Prostějov (KP) - ref. KPM4813
Though the question: a rebox from the Fly kit (link)? Yes if you refer to the Hannants advertisement.
Sources:
https://www.hannants.co.uk/product/KPM4813
https://www.facebook.com/kovop/posts/1291967567663756
Box art
Remember there's also a new tool GB IIb announced by Special Hobby - thread: link
V.P.