I got the Reprint of the 1937 Linhof catalougue today...

Maybe there is one hint that I have a Model I?... Technical data list lists 37mm Extension of the back... Mine goes only 26mm

And I found a Feature that was new to me and that is only in 10x15 and larger models... Lens stand is turnable...

Linhof Technika I 10x15 - Movement by xipho68, auf Flickr