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.
I'll second most of these suggestions and my two perennial favorites every time this topic reappears:
Maze War is a frantic combat shooter for up to four.
Snowball Fight is goofy fun for two. Can't find the dump online so I've attached it here.
snowball.xex
BITD, ANALOG magazine published an excellent public-domain alternative called B-Calc. Just found it on one of my old 5.25" floppies. Don't know if it would be easily converted to cartridge.
Nice to see that he's including two of the three games I basically gave him a week ago, but he's decided to keep the copy of Q-Bert that he claims doesn't work.
Darryl came back for a second set of carts and was just as pleasant to do business with. A straight shooter who communicates clearly, pays promptly and is a legit gamer!