DJ member pin

[polo59]

Hello, I need some help to learn more about this pin I got from my grandpa.
Year? Is it a common item? Know more about the manufacturers of this model (periods, series, ...)?
Mine is an "ASSMANN & SÖHNE", with "GES. GESCH.". Any idea of how much it's worth?
Here it is:

Many thanks for your precious help.
Cheers from France