One of the toughest questions in New South Wales philately.
I don't own one so cannot do a real life comparison.
The following notes from Hutson may help:
The lithograph has a flat appearance and can't be confused with early engraved printings.
The lithographs are rare. The detail in the design is clear and defined.
In the worn engraved stamps the detail is indistinct - the lithographs don't exist in this state.
The colour of the lithographs is a "pure medium blue, not Prussian but tending towards cobalt."
Check out Abacus Auctions and search so you can compare!
Hope this info helps
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EDIT: Post 3000 (just noticed)