(There's no video for Expo '99 Icons yet. Please contribute to MR and add a video now!)
Expo '99 set include 19 icons representing products that were shown at that expo conference.
Expo--99---Set.sit (74.45 KiB / 76.24 KB)
Expo '99 Set icons / compressed w/ Stuffit
Those are classic Mac OS icons.
Emulating this? It should run fine under: SheepShaver