The stamp indicates that your 800 was manufactured the 17th week of 1981.
Please consider adding your info to the 800 Owners Database...
And congratulations! Colleen is the best!
Artifacting is a technique to generate color in hi-res mode exploiting the limitations of an old CRT monitor.
This is an emulated screenshot, it will look even worse with real hardware, especially with an RF connection instead of composite.