I would welcome a rebuttal with a bit more behind it... let me make my case in more detail, and feel free to respond if you disagree with any of my points.
NPK is no longer the simple, single division company it has been historically. The housewares division earns about $1.90 in EPS (after taking out corporate overhead, which is small). The defense business is on pace to earn at least $2.50 in 2007 (you need to see their filings for detail on recent contracts won and acquisitions made). The absorbent products business should make some money next year, maybe $0.25, vs. what might be a -$0.40 loss this year. So before investment income ($1.20 a year), we get around $4.65 for next year on modest assumptions. If absorbent products realizes its full margin potential, it should earn at least $0.50-$0.75, but let's be conservative for now. So, I think a 15x P/E is quite conservative for a company growing as quickly as NPK is right now, but this gets you 15 * $4.65 = $70 / share before assiging any value to the cash. If you add the cash ($21.40 / share), you have a $91.40 stock. If you would rather include investment income in EPS, then you have close to $6.00 in EPS ($4.65 + $1.20 = $5.85). You can pick your P/E, but it won't be 9x (where it is now)... a 15x P/E = an $88 stock. All these assumptions could of course be wrong to some extent, but if you generally round down everywhere, you usually more than compensate for any disappointments.
I know the stock has been "cheap forever"... but when was the last time NPK posted a 67% sales gain, as they just did for Q2? The defense segment just posted about a 225% sales increase over the prior year and an 80% sequential gain over Q1, and it still has room to run as it grows into its new prime contract and acquisitions.