Thanks for that, Grant. A good illustration. You now have a vintage looking bass!

Looks like a lot of the yellowing could be down to UV/bright light exposure, as the clear pickguard seems to protect the TO from yellowing so it must be absorbing UV before it hits the TO.

It would be interesting to have three test pieces of wood with TO on, with two left outside. One protected from the sun but open to the atmosphere and the other open to both. The third is kept inside in a dark cupboard with some clear plastic over it (like a pickguard) to minimise the effect of atmosphere and light on it.