Kevron is a key tag manufacturer based in Melbourne, Australia. The company specializes in making high volumes of transparent plastic identification tags that connect via keyring to bunches of keys. Kevron tags contain small strips of paper which can be removed and written on to identify the keys the tag is attached to. You might want to open your Kevron key tag to access the strip of paper. Though some variation exists between various Kevron tags you should be able to open yours in just a few seconds.
Examine the tag. Look for a small slot to in the plastic or a latch at one end.
Insert a thin, rigid object into the slot and pry up the plastic cover. Alternatively, pull the plastic latch back until it detaches before prying off the cover.
Write your details on the paper insert and replace it back inside the key tag.
Firmly push the cover down. Clip the latch back onto the cover, if necessary.