Hello and welcome to The house of Chrome.

 You are looking at an older 1950's era AD-1 microphone connector / adapter used primarily on RCA & Electro Voice model microphones but also a few Japanese ribbon mics. RCA used a much wider thread pattern on many of their mics and stands so it was essential to have these adapters to mount an RCA microphone on a standard 5/8 X 27 thread desk or floor stand which the entire industry had embraced at that time except for RCA which continued to make an off size thread patter up until the mid 1960's.

 Pic # 2 shows this very adapter in an older 1960's RCA catalog I have.

 There's really no point in buying a cheap plastic replica adapter like the ones being sold on Ebay and Reverb for a few dollars less that can easily be stripped or break off in your mic which would cause a big problem. Be safe and smart. Buy an actual original metal adapter for just a few dollars more.

 As seen in pics # 6 & 7 this adapter fits on any desk stand and then allows the BK5A model, 44BX and 77DX model mic to be mounted.

 As you can see in pic the adapter has extremely lite cosmetic wear. 

 If you just need more than one please just let me know?

        MICROPHONES SHOWN ARE FOR DISPLAY PURPOSES ONLY AND NOT PART OF THIS SALE.

 As with all my items...