What is this alarm? I assume it's Cerberus Pyrotronics and from theb90s

That could be a Cerberus Pyrotronics remote speaker, but that basic design is used by a lot of manufacturers, & not just those in the life safety industry. Faraday, Federal Signal, & Wheelock are three other potential makers of that device.

I have a pic from Harrah’s LV that once had a 90s Siemens or Cerberus panel (replaced around 2018) that had a speaker like that, let me get it

Does it have a specific name?

When it comes to the listed brands (plus a few others), there’s these:
Cerberus Pyrotronics: SM25-C/SM70-C
Faraday: 2955B-0-21-25V/2955B-0-21-70V
Federal Signal: SPK
Honeywell: SC811A1023
Siemens: S-HP-C
(turns out Wheelock’s only has two screw holes unlike the speaker pictured which has four so I excluded it from the list)