What does Check Mark Button look like on Facebook?

On Facebook it is the design shipped in 16.0, shown above at full size. Older revisions are listed beneath it.

When did Facebook add Check Mark Button?

Facebook first drew Check Mark Button in 2.0, released February 20, 2017.

Meta Platforms, Inc. has shipped 12 versions of Check Mark Button. Each is dated, so you can see when the design changed.

Facebook 2.2

This is the design Facebook introduced in 2.1, shipped again unchanged. It was not redrawn for this release.

✳ marks a release that redrew this emoji. The rest re-shipped the design unchanged.

What does Check Mark Button look like on Facebook?: On Facebook it is the design shipped in 16.0, shown above at full size. Older revisions are listed beneath it.
When did Facebook add Check Mark Button?: Facebook first drew Check Mark Button in 2.0, released February 20, 2017.
How many times has Facebook redrawn Check Mark Button?: Meta Platforms, Inc. has shipped 12 versions of Check Mark Button. Each is dated, so you can see when the design changed.