[Freegis-list] unknown dataformat

[WHarms@bfs.de]

hi list,
can somebody name that dataformat ? 
The extension is SDF and i found an binary format called SDF from autodesk but no ascii example or so.

Here is the header:

    6  505   46
    1 BUNDESREPUBLIK DEUTSCHLAND
    2 SDF
    3 AUTOBAHNNETZ - SITUATIONSDARSTELLUNG
    4 1991
    5 19.3.91, NAME


mfg
walter