I think the telescopic slider is the component which would be different between the 4 and 5 speed.
I'm pretty sure those jockey wheels are non original.
When reassembling make absolutely sure the nut on the end of that telescopic arm is tight. It can easily come loose with terminal results for the mech. I covered mine with a big dollop of epoxy two pack glue and it got me through the Eroica.
Simplex TdF
I think the telescopic slider is the component which would be different between the 4 and 5 speed.
I'm pretty sure those jockey wheels are non original.
When reassembling make absolutely sure the nut on the end of that telescopic arm is tight. It can easily come loose with terminal results for the mech. I covered mine with a big dollop of epoxy two pack glue and it got me through the Eroica.