We met today this work by Bach with this strange time - strange to me as I've never met before this meter. Of course it is possible ... but I ask if someone knows another composition with this meter, not only by Bach.
(my assumption was that it is a simple 2/4 (ed. or better 4/8) where Bach ignored to write the sign for triplets as this would be obvious for everyone ...)
But now I've found the copy of the manuscript from Johann Christian Bach who wrote the time 12/16 for this Gigue.