Chris Hodges wrote:

Many places use a paint which also etches into the plastic, but the kits
are expensive. There are various "invisible" markers which normally
come with stickers for the deterence factor, but visible marking may be
more effective - unless you think you'll want to sell the kit later of
course!

The markers are usually UV fluorescent and yes, the police do go over
any suspected stolen items with a UV lamp. If it is visibly marked, and
the police turn up with something you have sold on, one hopes that you
(not personally, generally)have sufficient honesty to direct them to the
buyers. Normal procedure would appear to be to strike through the old
postcode, leaving it legible, but clearly invalidated and append the new
one. This applies to moving address too. This allows an amount of
backtracking if needed.

John Schmitt