setting up image directories? which path?

Hi, I’m migrating a wp site with an unusual directory structure. Images are in 2 places: the directory above the root of the weblog itself and the uploads directory.

/mydomain
/blog
image files (all in this directory)

I also see images here:
/mydomain/blog/wp-content/uploads/
which contains:
blog/wp-content/uploads/2006/
one folder per month, etc
blog/wp-content/uploads/2007/
the same.

I see that there are recent 2007 images both in the
/mydomain/blog/wp-content/uploads/2007/ and /mydomain

Guesses

First thought was they are symbolic links. But actually they are different files. Some images are found in one directory, but not the other.

Second thought was an image plugin. But no image plugins are active now (though the deactivated plugin WYSI-Wordpress is listed but unused).

Third thought was that wp includes two different ways of uploading images. But I can’t figure out what they are or where to configure them.

fourth thought is that thumbnails and main jpgs are in different places. But no, both are located in the same place. blog/wp-content/uploads/2007/
However, in the
/mydomain directory, NONE of the images are thumbnails. (That is probably significant).

I have a feeling that previously the website assets were arranged one way and then they were changed. But no, there are Jan 2007 images in both directories.

This is a genuine mystery. Do you have any ideas about how to figure this out?