This looks like a shipping container number: CSQ U 305438 3 1 0 G0 Owner Category freight container Serial number Check digit ✓ ISO 6346 Container length 10 feetft Container height and width 8 feetft × 8 feetft Container type General – Openings at one or both ends Links Wikipedia: ISO 6346 — en.wikipedia.org Wikipedia: ISO 6346 § Size and type codes — en.wikipedia.org Sources ISO 6346:1995 — Freight containers — Coding, identification and marking — iso.org