Rev-counter upgrades ( Smiths / UK Jaeger*only )  Surcharge applies...
Early electronic rev-counters were designed for use with either a ‘Camshaft generator’  type RV ( E-type Mk1 )
or ‘Points based ignition systems’ ( type RVI )  If you intend fitting Electronic ignition ( including 123 etc )
most early Smiths / Jaeger Rev-counters ( including ‘cable driven units ) can be upgraded to work with  
Electronic ignition whilst retaining the ‘RETRO-LOOK’ ie. once re-fitted only you will know of the upgrade !

The most popular upgrade is from Smiths type RVI v1 /  RVI v2  current loop system ( points ignition )
to RVC earth pulse system which will work with electronic ignition ( or points ignition if fitting electronic ignition later )

The second popular upgrade is from Smiths type RV ( camshaft generator ) E-type Mk1 etc  to
either RVI v1 / RVI v2 if using points ignition or RVC for electronic ignition ( which will also work with points ignition )

Smiths type RVI v1 to RVI v2... reduces / eliminates  loss of calibration / over-reading when hot !( common fault with RVI v1 )

Smiths type RN ( cable driven ) units upgraded to  type RVC ( clockwise direction only ) eg. Triumph TR range etc

Smiths RVC units can be re-calibrated to suit ‘wasted spark ( DIS ) ignition systems’ ( e.g. no distributor )

Upgrades to type RVC can be  NEGATIVE EARTH OR POSITIVE EARTH... Please specify which you require
( A connecting diagram will be included with all upgrades )         *UK Jaeger was made by Smiths