Generally, there isn’t much you can do when you’re collecting in a spoil pile. I normally label fossils as float, reworked material, or stratigraphic position unclear. In the case of fossils that are age-specific, such as C. angustidens, you can constrain the possible origin to some degree. However, you should always be careful in doing so because it’s always possible that the range of a species isn’t fully known and you may have in fact found an older or younger individual that would extend the known range. I think for your Belgrade angustidens, I would put Oligocene, likely from the Belgrade Formation, found in the spoil pile.
In some mines, you can trace back where the spoil piles originated by talking with the miners, but that is also a risky endeavor because then you’re trusting their recollection of where the material came from. I do recall there being some age distinction in the Belgrade spoil piles, but the Belgrade spoils are so vast that I don’t know if one could confidently make the claim that they know the age based off where the material was re-deposited.
Along the Calvert Cliffs, we can typically constrain the age of beach finds based on what strata are exposed at that particular beach, but even then you’re assuming relatively minor transport.