I would guess it is Gunze Sangyo .. somhow the Czech kit producers seem to like this range ...
OTOH according to Urban Fredricksson's colour chart Gunze H28 is Metallic Black while Humbrol H28 is "Camouflage Grey" (~FS 36622) which looks on my screen like a light version of RLM 02 or slightly darker than ALG-5 (http://www.colorserver.net/showcolor.asp?fs=36622)
Ergo ... I think Humbol is more likely (Tamiya XF 55/ Gunze Aqueous H311/Modelmaster 1733 resemble the same colour according to above mentioned chart)
HTH
cheers
Steffen P.S. As a He 112 fan: Have you build the Rest models He 112 kit? I would like to read a build report before screwing mine ...