This is a broken piece of a sword blade. It's of a low-quality steel and could stand to be tempered.
Blade Fragment price in Growtopia: sells for about 19 WL, buyers pay about 10 WL (median of 804 offers from community Discords, past 30 days). Live price chart and the latest buy and sell offers.
Recently sold at: CXWAVE, HVSALES, ABLEMN, LVKHU, WZJE