Use a software such as h2testw, and see if it is fake or not
I maked the second test. results :
Warning: Only 12065 of 255999 MByte tested.
The media is likely to be defective.
11.2 GByte OK (23692800 sectors)
496.2 MByte DATA LOST (1016320 sectors)
Details:148 MByte overwritten (303104 sectors)
0 KByte slightly changed (< 8 bit/sector, 0 sectors)
348.2 MByte corrupted (713216 sectors)
148 MByte aliased memory (303104 sectors)
First error at offset: 0x000000000ac04000
Expected: 0x000000000ac04000
Found: 0x00000001928f2000
H2testw version 1.3
Reading speed: 14.4 MByte/s
H2testw v1.4