The Australian Sentinal tank project was very advanced, but circumstances led to it's not being utilized.  Some 66 AC1 Sentinals were produced, a handful of AC3 Sentinals and at least one AC4 Sentinal.  All models are included for "What-If" scenarios.  All models are available to the end of 1946 in order to be used in hypothetical scenarios where Australia is invaded.*
*
However, be aware of the limited numbers of AC3 and AC4 models that were actually available.  Exact numbers are hard to come by, but it seems that it would not be too far off to say some ten AC3 Sentinals were built, and perhaps as many as five AC4 Sentinals.  However, the numbers could actually be as low as two AC3's and one AC4 -- all prototypes.  Therefore this formation should not be purchased in any but the most extravagant What-If scenarios.*
*
Note also that most, if not all of the Sentinals, including the AC1 model, never saw any combat.  They were used mainly for training purposes and home defense.  Therefore all Sentinals should only be used in the Pacific Theater, even though some of the original motivation behind the original Sentinal project was to send tanks to North Africa if needed.*
*
The AC3 was built using the 25-pounder gun because the 2-pounder used in the AC1 was acknowledged as inadequate.  At the time, Australia was manufacturing the 25-pounder, so it was basically the only choice.  When the 17-pounder became available, they began design of the AC4 utilizing that gun.*
*
If the USA had not been able to supply the numbers of tanks that it did to Australia in the Pacific Theater, then production of the Sentinal would have continued.  But with plentiful Stuarts and Grants from the USA, and Matildas and Lees from Great Britain, the need for a home-grown tank was just not the primary consideration.*
*
One should note here that Australia was the only country not to accept the USA Sherman for regular service during WWII.  However, some few specialized Shermans (the DD and the Crab) were used in the Pacific Theater, and Shermans were used in Europe by New Zealanders.  The Post-War Years did see certain models of Shermans enter active service in the Australian military.*