I posted this in the worst signs thread a while ago, but here is a SR180 sign that was actually only installed somewhere between 2013-2015 according to Google Maps (replacing a near identical older sign - someone must have forgotten to remove the SR180). I think there is a few still lying around near Dandenong Bypass as well.
As stated on Wikipedia there is a faded out SR181 in Wonthaggi, which seems like it is still there since at least up to Dec 2019 (most recent imagery from Apple Maps, GSV is 2018).
Also I remember seeing a SR112 sign on Glenelg Hwy in the last 2 years or so, I can't remember exactly where it was though.