After years of searching I picked this little gem up this week. It took a long time to find just one but now I have two. One for each side of the boom.
![bounce](images/smilies/free-jumping-smileys-593.gif)
These are actual porcelain enamel signs Bucyrus-Erie had on their Bulldozer cable controls from the 1940's - 50's
Here is the other one I have