This is a square(ish) steel Jewellery making or Silversmithing stake that measures approx 45 mm square.
It has rounded sides and ideal for raising and shaping metal.

It has been lovingly used by myself for the last 15 years and has recently been burnished and polished and is in excellent condition.
It has a square peg on the bottom that measures 30mm in length and is 15mm square.