This is a perfect trowel for fresco plastering. Unlike stainless steel venetian plaster trowels this trowel is made out of Carbon Steel and may live carbon mark on the plaster if over troweling. Do not worry that will not affect painting, but will give a signal to stop overworking the surface. That is much better then over trowel and block the absorbtion of water/paint causing problems during painting.
Keep in mind - fresco artists did not have stainless steel during the Renaissance...