Interesting Cliff. Both manufactured by Ohne Lüftung - Blau, with one made in Germany and yours in Western Germany. The stamping die configurations (top and bottom) are also different (My apologies to those justifiably annoyed by others with anal-retentive tendencies - either cap will effectively keep oil in the tank).
BTW - I have found sources for very nice OEL caps, but patiently hoping to find a US spec OIL cap.