Roman spear blades have a flat or diamond-shaped cross-section. In a few examples, the middle line of the diamond-cross-section blade becomes a slightly raised,
sharp mid-rib.
But yours appears to have a large rounded mid-rib so that its cross-section is roughly -O-. Is this correct?
This -O- form began on bronze spearheads in the
Bronze Age and continued into the Iron Age, including on iron spearheads. It was common on
Celtic spearheads, so that is likely what yours is. Whether it dates from the time of Ceasar, or from hundreds of years earlier, I don't know.
SC