Metal vs. Bakelite Lens Caps?

[landsknechte]

I've noticed that there are both metal and Bakelite lens caps available for the LTM lenses. Does anyone know if they were both available all along, or when each style appeared?

 

[payasam]

Can't tell you about the history, but I had a bakelite cap for an LTM Summaron 35/3.5 which fitted on the lens and inside the front of the FOOKH hood. Ingenious. Also shows how small that hood is.