Mystery FD mount lens?

I saw this photo of a girl holding an AV-1 but I can't identify the lens?

 

Anyone recognize it?

 

 

Edited February 2, 2021 by mike_sowsun

No idea what lens (could be a third-party, like Vivitar), but the chrome button is probably a "lock button" used when you set the lens to "A" for shutter speed-preferred automation.

A chrome nose lens would have a silver breech-lock ring and this one does not look to have one. Given the reflection of the finger I'd think there is a filter on the lens.

Agree with the replies above: silver button is AE lock for the aperture ring, and there is definitely a filter on the front of the lens (reflections extend over the name ring area, and the edges of the name ring engravings are blocked by the filter rim). You can just barely decipher "2.8" on the name ring: this combined with the large-ish steeply curved front element implies a wide angle focal length. Most likely a third party 20, 24 or 28 lens: Canon's own FD and FDn lenses did not generally have large silver AE buttons (they tend to be smaller and black).

It could be this lens.