From Hidden Palace:

Notes

The build date is unknown. A possible build date is September 12, 2003 given by some parts of the .elf file. The versions of the game libraries (IOPR270.IMG, etc.) are also consistent with a build date in 2003.

According to an anonymous source, it began as Twisted Metal Black 2 on the PS2, and a much later version was released as a bonus within Twisted Metal: Head On for the Sony PSP.

The loose files were copied directly from the hard drive of a PS2 development system.

A rebuilt ISO is included with this release. It is based on the loose files, and is improved from the two rebuilt ISOs which were originally part of this release.

The improved rebuilt ISO (Twisted_Metal-Harbor_City-Prototype-Rebuilt-63-Patched.iso) will boot in PCSX2, a PS3 DEX, or a PS2 Test.

The prototype behaves the same way in all three: the menus are functional, but attempting to start the game in MOST ways will cause the prototype to lock up. However, by using the “Dev Console” to select split-screen mode, most of the maps built into the prototype can be explored: Docks, Ghetto, Goth, Railyard, and SCenter. Selecting the Airport map will cause the game to lock up.

The menus in this prototype are somewhat confusing in that instead of a list of values, a given option will only show the current value, and must be cycled using left and right on the D-pad.