Ty, yes, it's sentimental, indeed.
I haven't used it since I discovered the crack, however.
On the sidewall, there are, what you call "LP grooves" (yours on the cooking surface, mine, on the sidewall). I think it's very cool.
The only problem I have with using a cracked pan (aside from liquid leaking out during cooking) is the potential for bacteria in the crack, so I suppose I'll just hang onto it. My mom (aunt's sister) is still with us, and she used that skillet since my aunt died back in the 80s.
Thanks for your thoughts.