There's a small subset of primarily (exclusively?) Sony camcorders in the mid 90s that used an "XR" badge as part of their video standard; Video8 XR or Hi8 XR. It's supposed to stand for Xtended Resolution, and I think it's all nonsense. I don't see how they can have any real format differences.
Now, it's possible this was marketing for a better CCD sensor or drive heads, and I would be interested to know any differences if they exist, but I'm mostly curious if there's ANY basis for this claim what so ever or if this was just being slapped on. The fact that there's Video8 XR models makes me think it could be. Then again, there was plenty of overlap where you could get Video8 HG tapes next to Hi8 MP tapes.