It's a cross between the old GTK and CDE
I have not created "from scratch", I just changed the color and some of the buttons.
The theme is similar to the ancient GTK style. Made on the basis http://gnome-look.org/content/show.php/gtk-motif?content=17191.
My advice is to use the icons and window borders
If you love retro, for better simulate CDE
Window manager border screenshot is Mofit-slim 1.0
Or window borders "microdec" of a standard set of themes xfce window
And the icons that you see in the second screenshot. It is very well suited for straight lines "in the style of CDE". Indeed, it is very similar, compare for yourself! :) http://www.guidebookgallery.org/pics/gui/system/managers/filemanager/cde15solaris9.png