From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Test results for a Smith's electric petrol gauge showing actual gallons versus gauge readings.
| Identifier | ExFiles\Box 61\3\ scan0256 | |
| Date | 29th September 1931 | |
| X4523 SMITH'S ELECTRIC PETROL GAUGE 29.9.31. TESTED IN 12.G.IV. PETROL TANK. 12 VOLT BATTERY. | Gallons. | Gauge Reading. | Gallons. | Gauge Reading. | |----------|----------------|----------|----------------| | 0 | 0 | 8 | 7.9 | | 1 | 0 | 9 | 8.9 | | 2 | 1.9 | 10 | 10.0 | | 3 | 2.9 | 11 | 11.0 | | 4 | 3.9 | 12 | 12.1 | | 5 | 4.8 | 13 | 13.1 | | 6 | 5.8 | 14 | 14.0 | | 7. | 6.8 | | | | ||