Two things this film did really well... (Spoilers)
1) The gorilla costume.
That costume is head and shoulders above any other gorilla costume of the era. It always baffled me as to why gorilla costumes were so impossible. This film got it right. They even had the interior of the mouth to look like a gorilla. It still requires a bit of imagination, but it's better than any gorilla costume until the 1970s. If the gorilla costume had been that good in King Kong Versus Godzilla (1963), my childhood would have been complete.
2) The violence.
I was surprised to see blood splatter against the painting in a film this old. Then the movie revealed that the ape had merely knocked over the paint. The model was across the room and yet unharmed. Still, for a second or two, your eyes saw what they thought was blood. And it showed just what was going to splatter a minute later.
The same goes for the scene with the mannequin. They couldn't show a woman being brutalized on screen, but they were able to show the ape's brutality upon a mannequin and let our minds connect the dots as to what it was like when the women were attacked. He even ripped the mannequin's shirt off as a suggestion of a possible sort of sexual violence.
It was the perfect way of showing what they weren't able to actually show.