So I watched videos and read some articles comparing the SM to the SM4, and every article talks about how they went from having 14 grooves to 17. Mine has 15 grooves. I bought the club used from a respected private golf club dealer. Everything looks normal, but the authentic stickers on the shaft were gone when I got it. There is a serial number on the clubhead, so how can I go about finding out whether this is an authentic club?