Bought back in February 2006 from a guy in the UK. Along with this Carmageddon64 cart I also got a Jeremy McGrath Supercross 2001 and All Star Baseball prototype, all for £100 shipped - man those were the days!
The most interesting of the lot however was this Carmageddon proto as it's not final. The car has massive gravity issues, it's like racing on the moon (like I know what that's like) and it also has a Build date of May 4 1999 on the pause screen - the game wasn't released until July 25 - 2000.
The build also has serious issues if an expansion pak is inserted, in fact it's only playable if the dummy pak is inserted. Another funny detail is that the prototype has 4 languages to choose from, but they're not funny translated... Okay so maybe that's not so funny after all.
Anyway a long time ago I made a small video which can be seen here.
There's a little bit of debug available if you press left on the pause screen you get some coordinates on screen, there might be more but I have not been able to find them.
That's all I have to report from one of the worst ever N64 games made (that I know of).