A worn die is not the same as a worn coin, and I do agree the reverse die had lost detail, a bit like some ‘F’ reverses in the penny series. I pondered this previously, why the need to mark the engraved face of the die to monitor longevity, when the die could be marked elsewhere in greater detail ; they would have to have counted the number of actual coins struck per studied die either way. And the die marked coins seem to have been too few to be practically monitored for ‘in circulation’ studies. Could partially worn regular dies be lettered or numbered to in some way monitor a later stage of their lives, or to be brought back into use? Perhaps with such a tiny mark the die would not even need annealing. Is there evidence out there?
Jerry