That looks like the lettering was done by a stencil like this one (
http://www.amazon.co.uk/Staedtler-572-05-Lettering-Transparent/dp/B000WL0XTK).
It takes a bit of practice to get anything as consistent as in the pictures - I used to use these stencils with a Rotring pen for cartographic labels back in my geography degree days. I'm not sure how practical it would be draw directly on the enclosure metal: perhaps use the stencil to write on to waterslide transfers or similar, then attach these to the box and varnish over the top of them?
I must confess I take the coward's route of the ol' Brother label maker or even just hand writing with a Sharpie myself.
Best of luck: there's no feeling like noticing that you've got the spelling wrong on the 20th line of a stencilled map legend.