It's not the fault of the coin. The visible letters stand out sharp and clean. Human minters failed. The flan was rolled by hand when the metal was already too cold, so a crack appeared. Mint staff tried to hide the crack by rolling over it again. They not only failed, but also made the part around the crack thinner, so that when the die struck, it failed to make an impression on the thin part. I can well imagine the repeated shrugging among the minters and their supervisors, paid by piece.
Meanwhile, you have yet another prize coin in your collection, illustrating the difficult task of balancing preservation and rarity. In those circumstances, the one shroff mark becomes an asset, not a liability. Here's a coin you would have bought anyway, even if it had had more marks. Now that there's only one, you can tell your visitors about shroffs and say "I have an example of a shroff mark right here" to your unsuspecting visitors.
Peter
