These two top images are a comparison of the edges of a 1912 matte proof (left) next to a 1912 business strike (right) coin. At left they are pressed together. At right they are free standing.
The edge of a matte proof will always be flatter, smoother, and more reflective then its more rounded business strike counterpart. A matte proof will stand alone on its edge very easily. Further,
the inside and outside edges of the rim, as seen in the images below with the matte proof on the left and the business strike on the right in each image, will be sharper and crisper. A matte proof will have its
inside edge drop off more steeply and therefore the coin will exhibit less of an inside curved dish than a business strike. A matte proof may also have a slight fin on the far outside of the rim around the coin.
In general a matte proof coin will have the following surface and edge characteristics to help differentiate it from its business strike counterpart:
• More detail in the image and design elements.
• A surface matte appearance resulting from the blasting of the die surface. Wear and toning may result in this surface being lost.
• Flatter, smoother, and more reflective rims.
• Sharper and crisper edges on the outside and inside of the rim.
• Less dishing of the coin than for a business strike.
To be absolutely confident when authenticating a matte proof coin you must examine the die characteristics for that year as described below on the obverse and reverse for the 1912 matte proof.
One die pair was used for 1912. For the early and late die states there is a die scratch through and above the date which I could not find.
For the early and late die states there is a die scratch through the ERTY of LIBERTY.
For the early and late die states a die scratch from the top of Lincoln's head below the WE.
For the late die states a die scratch above the TY of LIBERTY.
A die scratch from the rim to the left top of the first T of TRUST.
A die scratch above the O of GOD.
A die scratch from the rim above the E of WE.
A die scratch near the rim above and to the right of the second T of TRUST.
Two parallel die scratches between the I and the B of PLURIBUS. These are from a master reverse die used on matte proof
Lincoln cents from 1910 to 1914.
A die scratch from the lower right leg of the M of UNUM in to the area above the E of ONE. This is from a master reverse die used on matte proof
Lincoln cents from 1910 to 1914. A late die state heavy die scratch from the M of AMERICA down through the bottom of right leg of the adjacent A
to the left was not found.