I thought a lot of Grado models would share the same driver but they are (de)stressed differently. As in that they start out the same but when they are put into the final product they sound different due to the procedures they go through.
It wouldn’t surprise me if they updated models through their lifecycle such as the RS2e having both the black and brown headband. This could be due to them being a small manufacturer and certain components being unavailable after a while.
Edit - I am open to clarification on this though.