Very cool microphone in working condition. 
You are looking at a Shure Brothers 51 Dynamic microphone that is equipped with the Multi impedance switch. 
This 51 was manufactured in Evanston, ILL sometime between 1960 and 1964 before the 51 model changed to the black foam screens. This one was the 2nd generation 51 with black silk screens and was only made for a few years before the foam became standard. 
I believe Shure Brothers stopped manufacturing this mic in 1969 or 1970.
This is in Good Working and Cosmetic Condition, Click and Enlarge Photos for Details.
Very Good condition.
Buyer assume all shipping cost.
I expect payment within 2 days of auction ending.
For more details, please contact me.
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Good luck and happy biding.