It was sold in large portions at street stalls, about the size of today's onigiri. The fish originally wasn't raw but marinated in soy sauce, in order to be kept fresh.
EXIF info:
Nikon Df
Lens: 24-70mm F/2.8G
Focal Length: 54mm
Aperture: F/3.5
Shutter Speed: 1/60s
ISO Sensitivity: ISO 2000