Its a MY99 fork which means it was probably cast in 98 sometime or sometime earlier as the legs didn't change after mid/late 97. What gives it away is the polished legs and the decals. The triple clamp crown was also available in 99 to allow the fitment of the 1" steerer however it could be from an earlier fork - they were the same anyway.
For the record the easiest ways to tell the differences are as follows:
MY97: Introduced in late 96 and has red preload knobs which are round. The preload top caps also sit noticable above the crown where the stancions bolt on. These high top caps caused clearance issues on many frames and sometimes a Z1 crown was fitted to fix the problem. The Z1 crown being taller between the top on the top cap and the crown. The Z1 crown also has a large area where the stanchion bolt up and is easy to spot due to the wider bolt spacing for the stancions.
Decals have Z1/Z2/Z3 on the side of the fork down low near the hub.
MY98: revised top caps to remove the above clearance issue. Preload knobs chnaged from round ones to smaller ones with a squared off edge. Preload knobs are also blue on all forks except for red ones where they are red to match.
Decals have the Z1/Z2/Z3 script on the front on the leg just below the brace bolts.
MY99: Pretty much the same but an expanded range with air sprung Z2 Superfly with valves on the front which were next to impossible to get a pump on without removing the V brakes.
Decals have multiple lines at an angle for the length on the bomber script (just like the one in this case).
MY00: complete changes to the arch on the Z2 range except for a few bolted Z2 superflys etc.
Decals have there larger angled lines behind the bomber text on the lower part of the leg.
I can do photos and more detailed changes between the years if anyones really interested, but should keep you out of trouble for now