So not a part of the nostalgia crew, but maybe I should be since I started into the pc world around that time.
Anyways, I just acquired an older hp z200 that used that type of pci card retainer so this system was probably originally made by HP for Fujitsu/Siemens. Probably a solidly reliable machine though as we have Fujitsu POS systems in one of our businesses and they aren't your normal lga775s. HP workstations like the z200 are pretty hefty as well, so I'm sure this one is no lightweight.
The 5 bncs sticking out indicates a video capture or data acquision card of some sort. My guess is video capture. And as someone else pointed out--definitely missing a video card which is required with most xeons since they don't have an integrated video card.
If this is a xeon 51xx series and it is dual cpu, they can be decent to just use as a desktop. I have Dell and HP servers that have dual 5160s and they feel snappier than their i3 or lga775 equivalents (probably due to the sas caching controllers and 15k sas drives--they hit near ssd speeds when it's a cache hit). FB-DIMMs and 51xx xeons are a bit of a power hog by modern standards, but power is cheap, so just turn it off when you're not using it. At idle, my servers use about the same amount of power as my Dell i5-2500 with a gpu, so even if you don't turn it off, you're not killing the environment or anything.
Best thing will be to google the numbers on those stickers with the barcodes on them and then open it up to see what you have. More than likely you can put an older gpu in there even on the stock power supply with some adatpers, load it up with ram for cheap (FB-DIMMs can be as cheap as 50cents/gb shipped--and I know a source if you need some), stick a fast sas drive in there if it has an sas controller (you can usually run hardware raid 0, raid 1, and 1+0 at the minimum on a good controller for even more speed), and then install an OS and enjoy!
What I'll usually do when I acquire a system like this is to get it too boot and then use clonezilla to clone off the stock hd if there is one. That way, if I really mess something up, I can just restore the drive and get it working like I found it before messing with it some more. Good luck and tell us how it goes!