Sturmey Archer Gear indicator chain MK V
This chain pulls the internal hub gear to actuate a gear change (don't pedal as you change hub gears)
Sturmey archer part code / sales no: HSA420 - Gear Indicator MKV
This can be identified by IIIII carved into the the spindle (you will need to remove the indicator chain to check what yours says) - you will also need to remove the dirt covering the marking on your existing indicator chain
Alternative Products
These other products might interest you!