In the Mishnah Brurah by ois daled, it is written that the protrusion on the back of the top left of the daled is only lechatchillah le ksivah and a square corner is enough halachically to render it kosher.
By a reish however, many poskim hold that even if it is a square corner on the top right (instead of being round), it is not possul but rather a shailos tinok (see mishnas hasofer). A tinok will inevitably read it as a reish, even with a perfectly square corner) because he is used to the daled protruding on the top right.
So is this the only case in Sta"m where one tzurah can potentially be Kosher for two different letters? And how is such a phenomenon possible?