Vintage green army cap size small for large headed kids or small headed adults!

Vintage green army/military cap size small for large headed kids or small headed adults! As you can see from the pics, it will fits kid with a big noggin but I reckon it would also fit a tween, teen, or adult woman with a smaller noggin. Tag says small. Is it just really old and army men had smaller heads in bygone times? It’s possible. Super cute on a kid. My best measurement of the inside is about 20”. Imperfections noted in the pictures.