When the UN Specification Package symbol marking is slightly distorted, you must ask for the copy of the Test Certificate to verify whether the package is authentic. When the shipper purchases a UN DG package, the dealer will provide a copy of the Test Certificate. On the Certificate, an image of the UN marking is shown. You would need to check whether the UN Symbol marking on the package is identical to that of the Test Certificate. If the authority at a transit airport or at the destination airport challenges the authenticity of the package, you will need to get the copy of the Test Certificate to prove authenticity of the package.
As long as the Test Certificate is authentic, there is nothing to worry about. Only the last two digit of the year of manufacture is used, but if the image on the Test Certificate shows a full 4-digit year, again, the actual marking must coincide with the Test Certificate. For plastic drums, plastic jerricans and flexible IBCs, the UN symbol marking must accompany the month of manufacture.