034 is a multicolour from the Au Ver à Soie 1 fil range: a 1-ply "bouclé" (blending filament) metallic thread. On its own or combined with another thread, for example threaded through the same needle as strands of silk or stranded cotton, it adds bright highlights to embroidery on any fabric or canvas.
1 fil comes in around 45 colours in gold, silver, copper, plain shades and blends; the brighter Hi Lustre version comes in around 25. Photographs are only a guide: the sheen of metallic threads changes a lot with the light.