Production year appears to be 1999. Never been shot, is there any maintenance necessary before I put a few rounds through it?

O ring in the mag tube in front of steel rings. Check for dry rot and cracks

The older ones were good, not sure what the dates are determining good from not good, lol. but a 90's model should be ok. yes check the O ring, though I've never had to replace mine...only thing I did for mine was replace the magazine spring after many years, but being never shot you should be good

clean the dust out. some good oil

Been in a case for 27 years so I’m pretty sure dust isn’t an issue but the seal on the other hand probably needs attention.