Canon RC-251 model in Europe (iON) were commonly equipped with the Texas Instruments TC244a CCD sensor.
This sensor has 242 rows (lines) with 786 elements (pixels) on each line. So in silicon it can produce an image with at best 786x242 raw native pixels.
The TC244a uses a technology that interpolates the 242 pixels up to up to 488 TV lines , so at best this "Hi-band" circuit could produce 786x488 pixels interlaced.
When the image is stored onto a Video Floppy Disk the video-standards sets another limitation. The PAL-version stores 500 TV lines onto the disk. The NTSC-version stores 450 TV lines.
So, an image stored on a Video Floppy Disk can at best in theory be recreated in 786x500 individual pixels (PAL), but because of the over-scan and sync- related signal loss it usually result in images at 640x480 pixels when transfered to .png / .jpg . with full clarity.
Then, with line doubling techniques and advanced oversampling / treatment / processing we can get sharp images in 800x600 pixels and as best 1280x960 with reasonable clarity.