GoCLN Vitamin C uses DSM Vitamin C ingredients manufactured in Scotland. It is the only vitamin C currently produced in the West.
In today's society, the technology is sufficiently widespread, and L-ascorbic acid (the substance name for vitamin C) is scientifically comparable no matter where it is manufactured.
On the other hand, DSM has the longest history and experience in producing ascorbic acid, and I think its quality is more worthy of trust than the numbers. This is probably the reason why it is so popular all over the world. The manufacturer, DSM, is proud of its quality and is proud of its "QC" trademark.
Fuji Organics' GoCLN manufactures hard capsule products filled with DSM's vitamin C "QC" at a highly reliable factory in Japan.