I am about to buy some metallic silver welder's pencils on Ebay and see Verithin and Laurentien brands. Seems hard to go wrong with a pencil but noticed the Laurentien were about half the price of Verithin. Any reason not to go with the cheapest?
Just what is the purpose of this writing implement?
For marking on 'dark' metal (welding use or not), like mill scale on steel, I use either a welder's soapstone or a silver Sharpie marker. For 'serious' welds where contaminants like paint (which is what a silver Sharpie pretty much is) would/could be a concern, just the soapstone gets used. YMMV.