Now that Roswellite tm is being talked about I am getting a lot of questions about it and also microphone materials in general. It is satisfying to see that people are interested in this vital area of transducer design.
On the right is a shot of the shutter mechanism from an RCA 77DX ribbon mic which you can enlarge by clicking on it. The cam shaped yellow/orange part is made of a thin sheet of phosphorous bronze, which is an alloy, similar to brass, but with more spring. In fact there are many springs made out of this exact material.
I'm not sure why RCA chose this material, but I can tell you that I think it was a good choice: Not likely to corrode, flexible yet stiff, not likely to lose its shape over time. Sort of like what we want in a ribbon! But phosphorous bronze is, sadly, a very poor material for a ribbon, as it lacks the strength needed when it is made very thin, and it has rather mediocre conductivity which is quite important in a ribbon that works in a magnetic field.
I guess I went on and on at length about materials used in mics, in Lynn Fuston's Tape Op Con interview which you can find here. Motor mouth me must have had a good night before or something, as my usually laconic commentary is seemingly endless. If you can stand a 45 minute monologue, you might be amused.