How do I authenticate an LV strap?

[audi.19]

I bought an LV Alma handbag some time ago. It came with a strap which I believed was genuine. I am just wondering how I can tell if it is in fact real? It certainly looks the part but the length is 98cm, and I am led to believe that an authentic strap should be longer. Any guidance would be appreciated! I have tried to attach pics but for some reason I haven't been able to

 

[Elliespurse]

Hi, I think the best would be to post for authentication in the thread above here (you need to post pics at the same time though).

Is the strap adjustable?

 

[Elliespurse]

I also posted pics of different straps a couple of years ago here: http://forum.purseblog.com/louis-vuitton-shopping/vachetta-strap-where-can-i-find-one-545333.html