https://postimg.cc/gallery/yJZ4BRf

House was built in the early 1970s, so I presume this Sears Intercom is from around the same time. I have already removed the interior intercom and replaced it with a wall tablet. I am hoping to replace the exterior speaker with a video doorbell, but I can’t figure out how to remove it. It’s 5" x 3" and has no visible screws or recessed holes. I haven’t been able to find anything similar to this online. Any thoughts?