Conversation so far:
where is the border crossing card number located
The MRZ on the BCC is on the reverse side. The document number to be used should be the second set of numbers after the Country of Issuance.
who is the border crossing card issued to
The BCC is issued only to Mexican citizens residing in Mexico and by the U.S. diplomatic missions in Mexico

Question: for how long is the card valid
Self-contained rewrite: for how long is the border crossing card valid