200-100 BCE Alexandria Egypt. Floor Mosaic Roundel: A Dog & An Overturned Gold Vessel. The quality is fantastic, and this period represents a high point in the mosaic craft in the Greco-Roman world. Many of the tesserae are only 1-2mm across, which allows the mosaicist to achieve a painterly effect. The technique is called "opus vermiculatum", or ‘wormy work’. The Greco-Roman Museum in Alexandria. I can't help but wonder if this wasn't the inspiration for RCA Victor's "His Master's Voice".