LNL = Lawrence National Laboratory for a start.
There are 250,000 google responses to LNL
Three letter domains are rare and very useful. Three letter domains usually go for low $xx,xxx to end users but some can go much higher. It depends how good you are as selling the domain and how badly someone wants it.
Consider:GED.com, $150,000; SSM.com, $145,000; OLT.com, $93,000 and GLU.com, $75,000
Also, On eBay FZB.COM got only a single $2500. bid. xii.com went for $1825.
If you need quick money you will probably not get a lot for it. Placing it on SEDO with a $1k of more opening bid and no stated price and seeing the traffic will tell you something. EBay is a crap shoot unless you have several interested buyers at the same time and you want to sort it out. There have been really high sales on eBay but I feel that those were orchestrated. I can't imagine a $600,000 sale just 'happen' but it happened...
Dave44