iPhone 4 earpiece models

I replaced the earpiece of an iPhone 4 and the new earpiece did not work.

The earpiece on the iPhone 4 is a little different from all the earpieces I can find here on ifixit or ebay. The pins are about half the legth and the serial code is different too.

So I am wondering if both earpieces are compatible. Has anyone experienced this?

This iPhone is a Softbank iPhone 4 (sold in Japan).