Dual 4K projectors for passive 3D or any of the 4K LG passive screens from late '13-'16, and possibly a few Active 4K screens. Samsung had a few that displayed 4K 3D.
For 4K LG screens they can accept 4K 3D signals up to 4096x2160p. In order for the screen to display the highest quality (and use all screen area without black bars) you will have to render to top/bottom 3840x2160 which will show with passive glasses 3840x1080p/eye. This is half 4K/eye but double the resolution of Blu ray 3D. This looks very good in 3D on OLED.
Dual projectors you would have to ask around there are a few on here using dual projectors but that method you would have full 4K/eye, content is of course non-existent commercially right now.
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