1. the submission of either documentation of an export certificate from Canada, or 2. documentation of provenance (owner and collection) and showing that the coin legally left the country of origin. This is the first time that I have encountered this issue. Apparently the letter was selected for examination by CBP officers (such an honor!). It also appears that this coin is classified by CBP as an "OLD COIN +100 YRS / YEMEN". Does anyone have suggestions for next steps? Thanks!