I have reviewed as many aging guides as are on the market. While it is easy to identify a fawn, 1.5 year old, and a 2.5 year old or older - it gets tough figuring out the other ages. My taxidermist has mistakenly thrown away the jaw bone for my deer TWICE! He's always apologetic, but I think a third time he might be tempted to do the whole switcheroo.
BTW... This is the best aging video for 3.5 and older I've seen.