H/T Rabbi Mordechai Honig for finding this 15th century Ksav Yad on Rashi for Bechoros 38a. Our modern editions have “Chilazon” as “Limon” (almost like a lemon). Apparently this was a misprint, aaaaaand….. it’s yet another reference to Limetz/Limace (snail)! So much for it being a snake or berry! Furthermore, here’s the full context/translation (courtesy: Sefaria): https://www.sefaria.org/Bekhorot.38a.21?lang=bi&with=Rashi&lang2=en “one may slaughter a firstborn animal outside the Temple if there was in his eye a cataract, a tevallul, or a growth IN THE SHAPE of a snail, a snake, or a berry that covers the pupil”

The Ksav Yad clearly showing it’s Limetz/Limace, which means snail. It’s not a Nun Sofis which you can see in many other words on this page.

Another tzadi sofis example. Notice that the point shoots to the right as opposed to curving back left.