Made in sections, the triangular design has been cut out using a hand punch.
It is first lined with an "Antique Gold/ Bronze" leather (actually it has the same color as the solid brass saddlery buckle that you see. It really adds depth to the cut outs without been too "sparkly", subtle is the word.
Lastly it has been backed with a pigskin suede.
This guitar strap consist of a few layers of leather. Pictures sometimes speak better then words more details here Strap in Construction ( it will open in new window ).

With this one, it is also possible, should the need arise to easily make it shorter by taking one of the sections off, which would bring its length down from 41 1/2" to 46 1/2 ". If you intend to buy it, run it past me .and I'll be happy to do that modification for you free of charge.