The Fast Reverse Button emoji is two overlapping triangles pointing to the left. On older devices, this was a way to rewind tapes and cassettes. You don’t really see this button a lot now since you can just drag a slider to move back in a song.
The fast reverse button emoji was introduced in 2010 and released as part of the Unicode 11.0 standard. This emoji can be found under the symbols
category. Because the fast reverse button emoji has been around for quite some time, it should display correctly in the majority of operating systems.