Find your Content Central version
The three places the version shows — the login page footer, System Health's installation details, and the Classic page header — and which number to read to support.
Thirty seconds to the number support will ask for — from any of three places, signed in or not.
Without signing in
The login page footer carries it, after the copyright line — like v7.8.10132. The fastest answer when the question is "what version is this server?" and you're standing at the door.
Signed in, with detail (administrators)
Administration > System Health — the Installation details section is headed with it: "Content Central 7.8.10132.0," and expanding it adds the application and database schema versions. This is the most complete answer, and the one to read off when support asks — especially after an upgrade, where the schema lines confirm the database came along.
On Classic pages
Any page that opens in the Classic interface shows it in the header's top right: "Content Central v7.8.10132."
The same version renders slightly differently by surface — three parts with a v on the login page, four parts in System Health. They're the same build; give support whichever you're looking at and mention where you read it.
Success check: you can answer "what version?" without asking anyone — which, next to an upgrade or a support ticket, is exactly when the question comes.