Thanks - the finish is achieved with bladed end of a panel pin hammer over the worked areas of the key to soften the transition from the raw cast area, then buff on a bench mounted wire wheel applying more pressure in the unworked areas, and finally a wipe with some wd40 to stop it oxidizing before handing it over to the customer.

Personally I prefer to try and preserve the cast look and blend the worked area back in, I have finished entire keys in the past and given that some of the cast keys we get can be like a banana you end up removing so much metal to make it 'perfect' but then the end result loses it period charm I feel.

In this case the customer has several traction engines and so a comprehensive work shop, I suggested they try hot dipping it in some old oil (we used to call it bluing when I was a lad, but thats something else now) for a darker finish and some protection, he was going to give it a try and let me know...