Found when cleaning out the garage. It slides to open up as shown in the photos.
It's a NEUMAN chimney cleaning tool from 1929
This chimney sweep tool is shaped rectangularly to match the inside shape of the chimney, and the expansion adjusts to match a range of chimney sizes.
To convince a spouse to keep it, you can rebrand it as a uniquely re-purposed flower stand:
No additional brushes or bristles are needed. The zig-zagged bottom is the brush. According to its 1930 patent, "The lower ends of the scraper bars terminate with transversely disposed fluted portions 6, which portions form contact brush elements for engagement with the four walls or" the chimney."
More details in the patent, at https://patentimages.storage.googleapis.com/bf/ca/9d/c4c933a9e6bf2c/US1775969.pdf