[JohnFen]

> I have not the foggiest clue how it is used - but I cherish it.

It's easier and more straightforward than you might expect. I encourage you to learn to use his slide rule, in large part because you might find it fun, but also to honor your grandfather's legacy.

[marai2]

I agree. In fact you should make a (YouTube?) video showing the slide rule and how to use it and your grandfather’s history to preserve this bit of history for your family and family’s future descendants.