I'm stuck. Which dime coin to keep for my set? 1924-D EF40 graded or 1924-D AU50 cleaned/details also graded.
Depends on what's already in your set. The XF40 is the easiest choice if you want a problem-free set, but if your set includes cleaned coins, you could do either as they are likely about the same value.
How can anyone answer without pictures? And why are you keeping a dime for your Lincoln set? Some "cleaned" coins you can't hardly tell, and others it's obvious and obnoxious, and still others another TPG would straight grade. My avatar coin was graded "cleaned" and they were wrong. It's now in a straight-graded holder.
Personally, I would keep the 1924-D EF-40. Pictures would be helpful but I don’t like details coins in my sets. But I do have one question, why do you need to keep this DIME in your LINCOLN set?
I avoid "details" grade coins. Not that I have not bought one that might become that if it were resubmitted. I just bought a 1799 large cent that could be in that category. In general, I would go with the straight grade. That goes double if the EF-40 is really solid for the grade. The amount of "meat" (detail) should not be that much less for "real" EF-40.
