I have one site in boggy ground that is really hard on non Silver coins. I have dug a lot of Buffalo, Liberty Head/V and Shield Nickels there at depth that were 22 TID. Some really deep at 20. Same with Copper Cents. Some as low as 36.
Condition wise they aren’t worth digging but of course I do anyway. Part of the reason for the low TIDs is from using mostly M3. The point is that in bad conditions TIDs will suffer. In better ground 25/26 is almost always a Nickel just like Jeff states.