Dreamcast Release of a US Dreamcast prototype for "Ecco the dolphin defender of the future (V1.005 2000.06.01, to be confirmed).

[Sega Dreamcast Info]

I didn't see anything special. The date is well before the final version but the build version is after. The final version, according to the TOSEC of https://archive.org/download/tosecdcus20190822 is 1.000

You can find it and download it on this page (with a NEW next to it)

https://en.sega-dreamcast-info-games-preservation.com/releases-exclusives-au-site