Another Fake shure guide for you to read.
I had a similar experience. Bought one on Ebay - but I had checked a real one out in a real shop first.
So what is there to look out for.
Well dont assume that the glossy box and orange warranty cards means youre okay - your not.
The differences i noted were that -
1. Around the neck of the mic, where it says SM58 - the one I got on ebay had SM58 on a sticker hugging the neck - AN OFFICIAL SM58 has the words printed around the neck NOT on a sticker , but on the body . SO IF ITS A STICKER - ITS A FAKE!
2. The other thing I noted was that where the XLR input goes into the mic body [at the b ottom of the mic], the three pins you can see inside the word shure and ther numbers 1 2 3 on each pin. The FAKE ONE did not have these markings - it had no markings at all.
3. A new one boxed comes with a cool SHURE sticker. My FAKE One came in the box with warranty cards but no sticker -
4. Official one also came with a cloth cable tie.
5. The black bag that my official MIC came with - was made in China. It had a little white tag inside.
I was fortunate that the sender did not send the mic recorded , so I told them it hadnt truned up and I'd had to buy another one. I did send it back for a refund, but if I hadnt have checked, I would be none the wiser. I cut my losses and got one from an offical source.
I have bought another one since.. second hand, and this one seems okay. Ticks the right boxes.
My advice to you would be to NOT buy one on eBay unless you can be SHURE [ yes a great pun I think as well] its an offcial product - the official ones seem to be more expensive obviously. Also, go for an unswitched one. More professional, and the fake ones seem to be all switched. Though I cannot be 100% certain on this.
Good Luck .