They are an IS mount. 51mm between centres.
other standards existed at the time including formula which was a smaller distance between centres and post mount where the holes are turned and threaded.
SID didn't come with formula mounts, not many forks did and not in 99.
you need the adapter...
This is how I made my disc brake adapters to run 210mm rotors on IS mounts to IS caliper (Formula B4) when the brake was designed for 180 front and 160 rear.
obviously without the brazing. I made the cardboard template in plywood though, so it could be tested (ish) before milling it from...
VIN plate and E11 can ( and should be) removed using IPA (wash it down the tube so it gets behind the vin or use a syringe and needle) and dental floss pulled down to get behind the sticker.
They don't care anymore. Rock up with a battery grinder in Broad daylight and take 60 seconds to destroy any lock. It's why I also go with making it look unworthy of the effort or two locks, so the bike next to it looks easier. 🤣
Over the seatstays and through the wheel with the upright of the post as well obvs.
Make it as hard to get to the D and the shackle as possible. It's why I like the 3/4 size locks they don't leave enough space to get a lever in.