A shipping paper lists one material as 'UN1203' and another as 'NA1993.' What does the difference between the UN and NA prefixes tell you?

49 CFR 172.101(e) — identification numbers column

Responders and dispatchers use the UN/NA prefix to know whether a number is globally recognized or only valid domestically (plus Canada). Hauling an NA-numbered load overseas can get your shipment stopped since the number isn't recognized outside North America.