| System | Period | Rows | What it dates |
|---|---|---|---|
| Country mark (lower bound, NOT a year) | the requirement applies from 1 March 1891 (Tariff Act of 1890, also known as the McKinley Tariff) | 2 | A country mark is only a LOWER BOUND (the item is no earlier than the introduction of the marking) and never a year. The single hard statement for thi |