Belongs together with post #207599. Which of the two should be parent?

The other one. It's older~

this one, she hasn't gone as far so it probably comes first

Exactly my thoughts, both comments.

I browsed the wiki and the forum quite a bit to find a guideline.

Azure4488, thanks for the artist tag. What is your source of information?

NuclearArbitor is correct. When an image was posted is totally irrelevant. First criterion for parenting is sequential order if two images come as part of some sequence of images (but now that we have pools, you should technically be using a pool for this, not parenting). Second criterion is file quality, i.e. how bad the jpeg artifacts are, if any -- the file with better quality should be the parent. And the third criterion is image size (dimensions) -- the larger version should be the parent of the smaller version.

The priority of these criteria is basically in the order I listed them, but like I said, the first one is sort of iffy now that we have pools.

Katajanmarja said:
Azure4488, thanks for the artist tag. What is your source of information?

Whatever it is, the artist tag eventually led me to post #355438, which had copyright and character tags. Further bits of info on Anime Characters database, and there you go. :)