From Wikimon

This card states that it has a D-Arc ID, but the ID number is missing.

I assume it's the '457' at the side of the card, but I honestly have no idea so maybe someone who's more familiar with the cards can answer instead. I've been largely ignoring the D-arc ID things when I'm going through the cards :v --Garmmon (talk) 03:39, 10 September 2015 (CDT)