Outdoors, many inspectors in this area (SoCA) won't accept felt pen as a permanent marking. It virtually disappears after some weathering.
Instead, they'll accept the use of the "paint pen", which applies enamel, and is just as easy to use as the felt pen.
Many labels won't withstand the test of time either, the adhesive loses its grip, and they fall off. The newer style of labelmaker is better for this, but the ink doesn't stand up to UV very well; it fades fairly quickly.
