This is a Tecomec OEM part number1029001E spinner anvil and is for spinning together 3/8" & .404 pitch chainsaw chain.
This anvil (insert) works with Oregon, Tecomec, Efco & Windsor bench mounted chain spinners and replaces Oregon part# 38597 and is compatible with the Central Machinery model 99835 combo breaker and spinner. This insert is sometimes referred to as the "A" type anvil.