Identify the tip polarity on this AC adapter without plugging it in
I have a 230V AC-DC adapter/transformer from Europe that I am trying
to replace with a 120V version.

No it isn't DC out it's AC out - hence the little squiggle symbol: &quot;~&quot; after where it says 24V i.e. 24V~.

I am trying to determine the tip polarity of the DC output.

The important things I've highlighted in red below: -

In summary, the output is AC and not DC - so you can plug it into your AC supply and determine this - operating below 230 volts won't hurt it. But if there's any doubt, be prepared with an oven glove handy and a metal box to pull it from its supply quickly should the marking I read be incorrect.
One further point and it may or may not be important - if you are trying to replace an AC adapter for something, the &quot;something&quot; may indeed require 50 Hz for some timing requirements and, if you are running at 60 Hz, you may get unusual results.