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 coils with standard and production ballasts.
| Identifier | ExFiles\Box 45\4\ Scan021 | |
| Date | 11th September 1922 | |
| RR. 238 (300 Bks.) (SF 152. 6-11-18.) MP 197880 ROLLS-ROYCE LIMITED. INSTRUCTIONS. To E.F.C. Order No: P.B. 48 Customer's No. X 40790 With Standard Ballast. Coil | Speed | Volts | Amps. | Max Gap. B | 500rpm | 7.89 | 1.12 | 6.5 mm. G.9. | 500rpm | 7.92 | 1.10 | 4.5 mm. With Production Ballast. Coil | Speed | Volts | Amps. | Max Gap. B | 500rpm | 7.97 | 1.06 | 6.5 mm. G.9. | 500rpm | 7.95 | 1.12 | 4.0 mm. Signed C.A.P. This Sheet must be filed on completion of the work. | ||