About people’s previous sets of collected shells, I would like to say, try to be absolutely sure that you never could have mixed shells from one batch with shells from another batch. That can easily happen when you are comparing shells from one place with shells from another place, perhaps in order to try to determine whether the identity of the species is the same.
Also, with any individual valves of bivalves you have, it is always a good idea to photograph the interior of the valve as well as the exterior. That is because the details of the hinge line and muscle scars are diagnostic in bivalves.
And, when you start uploading your older seashell obs, please ping me so I can look at them.