Still sounds like a 'new' tank to me.
Interesting seeing your photo though, i put a photo of my slightly newer tank on here a while back and you can see how theyimproved the drainage holes around the cap area.
Any of the tanks will fit your bike by the way.
98/99 18 litre
00/01 20 litre
02/03 22 litre
The latter tank will be a slightly different shape, but only on the upper part, it will still sit okay where it matters lower down.
Only thing is you still have pipes going downwards, whereas from 2000 onwards they fitted a rubber cup for the small metal excess/vent pipes to sit in to. It just means you don't get the possibility of kinked pipes when removing or lifting the tank.