There seem to be a lot of cheap SONY microphones on ebay at the moment. They are not always apparent from the listing especially when a stock photo is used or the item is located in the UK, instead of "fake capital of the world", Hong Kong. I recently bought a SONY ECM-DS70P for around one third of the RRP despite my suspiscions as to the authenticity of the advertised product.

I did not have a genuine mic to compare it with and so was unable to evaluate the audio quality*  However, there are several physical characteristics that give the item away as a being counterfeit. Below are two photos of the ECM-DS70P; the top one is the genuine SONY item, the second one, a suspected fake. Apart from the general cheap look and feel of the item (not always easy to see from a photo) some of the dimensions and subtle design features are incorrect. For instance, the mesh of the microphones should extend outwards further (around 4mm) beyond the silver plastic part of the body. Also, on the genuine item, these silver parts and mesh are profiled with a gentle curve and are set at an angle, unlike the fake version where they are simply straight and square. It would also seem that the jack-plug surround should be the same colour as the main body of the mic whereas with the fake item this may be a shade or two lighter. There may be other "giveaways" too but they may be less obvious, like poor quality moulding and cheap screws, etc...

* Other ebay members have since contacted me suggesting that from their experiences, the fake mic gives poor stereo seperation and distorts earlier at higher volumes.

Good Luck...