| System | Period | Rows | What it dates |
|---|---|---|---|
| Wardonia — a typology by the distance between the guide posts (1929 / 1933) | c. 1929 → 1933 (the transition), then to the end of production (the end year was not found) | 6 | This is a rare case of a typology that gives a direction of time: 1929 — posts wider than usual, 1933 — a switch to posts closer than usual. There is |