Chinese container production is concentrated in a small number of large manufacturing groups, each running several plants, clustered near the export gateways in Jiangsu, Zhejiang, Shandong and Tianjin. Below them sits a much larger population of workshops that modify and convert containers but do not build certified new ones. Telling the two apart is the whole verification problem.
The groups that build new ISO dry containers at scale are few, long-established and organized around carrier and leasing-company demand. Their plants run continuous lines with robotic welding cells, modern paint halls and an on-site survey function, and their annual output is measured in hundreds of thousands of TEU.
Around them is a wide layer of fabricators and conversion workshops. These do valuable work, and some of it is excellent, but a workshop that cuts doors into used boxes is not a plant with a type-approved design and a classification-society survey arrangement. A listing rarely makes the difference obvious.
Four things. A type-approved design, tested under a classification society for stacking, racking, floor strength and weatherproofness. A per-unit survey arrangement that ends in a CSC plate. A paint line capable of the primer and top-coat system the guarantee is written against. And an ISO 6346 serial number allocation, which a workshop does not have.
A plant that has all four can hand you a document trail. A fabricator will describe one.
Jiangsu, Zhejiang, Shandong and Tianjin carry the bulk of new dry container output, for the simple reason that a finished container has to reach a deep-sea terminal on a truck. Inland production exists but the haulage cost works against it, and it shows up in the quotation.
Regional concentration also explains lead-time behaviour. When export volumes surge, the same terminals congest and the same plants book out, so lead times across the network move together rather than plant by plant.
The manufacturer building your units is named in your contract, with the specification sheet annexed to it. We do not put plant identities into marketing pages, because allocation arrangements are commercial terms rather than advertising, and because a name on a website is not verification anyway.
What is checkable is the paperwork: the classification society, the survey record, the CSC plating and the serial numbers on your actual units. Ask for those from any supplier.