Compare the picture of the model you have with one from the
internet, there are clear differences between real and fake ones.
Also Ping putter have a serial number engraved on the face or
hosel, check this with Ping, or if it doesn't have one it is
fake.
To find a fake ping Golf club check the serial numbers (if it
has any) with ping themselves, or you can compare them to images of
the ping website, Or post photos of the alleged fake item on GOLF
WRX forums.