Note - some side lamps may have space to fit 2 incandescent bulbs, but the problems here are the amber bulb has to compete with the white bulb, so the amber flash is less distinct, and the increased electrical power draw. This bulb only displays one function at a time and consumes much less power.
What a fantastic solution!
To be a practical and safe vehicle, flashing amber indicators are really a must, especially if you want to drive your vintage car at night.
These newly developed LED bulbs are the perfect solution. You get to keep your classic side-lamp, such as the Lucas 1130 but add an indicator function without having to bolt on an incorrect, non-period accessory. White light for the sidelight position marker, with a super-bright amber indicator function in the same bulb. BA15D bayonet base (BAY15B base also available - see this guide to see which you need). This LED bulb work with 6vor 12v systems. Part number CSILEDW
Don't have a double contact bulb holder in your lamp?
Buy part 424 or part 1130BH-DC to replace your old single contact bulb holder. Now you can improve your visibility and safety whilst keeping the correct period lamps.