+1. These are models designed for small women. The 24" front wheel permitted a lower standover height using traditional lugs and a horizontal top top tube. It also allowed a shorter top tube, without severe toe clip overlap with the front wheel.
The subject model is likely a circa 1987 model. Pics may allow me to determine the exact year. The serial number is not any of the recognized Nishiki formats.
As stated, there are different 24" wheels. Most of the proportional women's bicycles used the 520mm version, as opposed to the 540mm. To ensure this is the correct size simply take a tape measure and determine the distance from the centre of the fork dropout to the centre of the brake pad mounting bolt. This dimension measures 269mm for the 540mm wheel and 260mm for the 520mm wheel.
520mm tires and wheels are still available, though selection is limited.