| 28S16976 | U1725 | MINISTRY OF DEFENCE AIR DOMESTIC R FERENCE NUMBER USE ONLY |
| A55 | K7766 | BRITISH STANDARDS INSTITUTION |
| B06005 | K0207 | HALE HAMILTON (VALVES) LIMITED |
| E6 | K7766 | BRITISH STANDARDS INSTITUTION |
| A55-E6 | K7766 | BRITISH STANDARDS INSTITUTION |
| A55E6 | K7766 | BRITISH STANDARDS INSTITUTION |