How Can I Test To See If I Have A 1946 Transitional Nickel?

You have that backwards. Acetone leaves a residue, which is best removed using IPA.

And 99% isopropyl is made for cleaning and/or drying electronic parts. It removes oils and water. It doesn't have random chemicals as the 1% - more often than not, because of the hydrophilic properties of isopropyl alcohol, the bulk if not 100% of the 1% is water.

It is far more likely that any residue you might see from iso is either from materials dissolved from the surface of what it was applied to, or from whatever was used to apply it.

Furthermore, 99% Isopropyl alcohol is completely neutral PH 7. No corrosive properties, either acidic or alkalinic.

Testing my SG methodology, using a silver quarter and a 95% copper penny:

Silver quarter: dry weight=6.082g wt in water=0.594 SG= 10.23906
Copper penny: dry weight=3.101g Wt in water=0.348 SG= 8.85387

Both are within 1% of their respective standard. I tested with a few more of each and was within 1% of standard each time.

Exact same methodology gives SG of wartime nickels (I tested all I have) mostly at less than 9.0 and frequently less than the 8.92 standard for non-wartime nickels.

The non-wartime nickels I tested as a control, test out between 8.89 and 8.93 or within 1% of the standard 8.92.

None of the wartime silver nickels are giving SG within 1% of the 9.25 I'm told should be the standard SG of a wartime nickel.

My methodology has proven reasonably accurate. What's wrong with this picture?

Specific Gravity is proving to be inconclusive.

Were there any known annealing errors in 1946 nickels? It does kind-of look similar to later Jefferson nickels struck on planchets with annealing errors.

I don't think it's from post-mint heating or living through a fire... but what do I know?