Your COA is GB/T2520-2008, but I receive GB/T2520-2000 by English language and GB/T2520-2008 by China language.
I would like to know your standard tinplate actually is GB/T2520 – 2000 or GB/T2520-2008 .
It is most important that your standard tinplate actually is the same specification which you supply on COA , because Custom Vietnam will check between tinplate actually and the information on COA.
Best Regards