I looked in the Genteam gazetteer without luck. I tried both spelling variations: names beginning with Lew and Sew, also tried Lev and Sev. I looked at names contain syn … no luck. I wonder if it a mis-spelling.
Sudety, I think is Sudetenland. This suggests either Bohemia or Moravia, possibly Silesia. It seems odd that would be used for post-war Czechoslovakia, unless, perhaps, the identity card is not Czech. Many people from Czechoslovakia fled to the west as the war ended.
Edit…
Perhaps posting an image, unless your great-aunts are still living, might give some other clues.