Labels (or Tags) mean a few different things in the track-and-trace world.
Direct Thermal Labels
The LP 2824 or GK420d for example use this model, where the labels are basically burned.
You can test for Thermal / Direct by scratching the label with a penny or key, it should make a black mark. Sometimes, rolls of these Thermal / Direct type labels will not print, because they are defective, use the penny test.
The [Dispensa-Matic Flex-Matic](http://dispensamatic.com/flex-matic/) label applicator enables the user to label all kinds of flat objects by simply setting the desired spacing using the digital readout and guides.
Just a list of vendors, not an endorsement.