Debbies - You are correct in considering the age, or year built, in choice of comparables, sold and active listings. Based strictly on the info provided in the two examples, it is highly unlikely the older home will appraise for the amount listed due to the age difference of the two and square footage difference. Then again, perhaps the newer one is grossly underpriced for the market area.
Now, yes, there are many unknown factors that would be required to accurately determine a realistic list price for both properties and appraised value of both, but it appears to me proper due dilligence on the part of one or the other listing agents, or possibly both, was not done in determining the list price of one or the other. Perhaps both have the same listing agent, or perhaps there was an input error in one or the other listings.
End result, it is very observant on your part and wise to question such discrepancies. You should be an appraiser!!!