That's really cool. I can't even imagine how you would go about making those pens, but, if I was an Iron Worker, I would want one!
You might want to ask them to introduce you to some other local unions in the area. You might be able to sell special pens to the bricklayers (cast brick dust), carpenters (wood, haha), elecrical workers, wire or copper, sheet metal workers, an aluminum blank, etc. Part of my career was spent setting up health & Welfare and Pension trusts for unions and they are a close group.