So I've been watching the Cracking Videogame Passwords series by Bisqwit who disassembles NES games and looks at how the password systems work (variables stored, what happens if you change these outside of standard obtainable values) and in the River City Ransom episode they found something rather interesting; a developer password:
Spaces to fill each row, seems to be a typical dev password; max stats, changes player 1s name to Shin and inventory has all technique books. From a trivia point this is the only valid password that uses the space character.

Bisqwit did not find any results for this password in google but the cutting room floor has since added it to their article (btw, other interesting things in that article are an easter egg that doesn't work properly in Street Gangs and the unused text line "My name is Shin").

As for the passwords odd letter structure, the Japanese passwords are 5/7/5 like Haiku.

Searched river, found no threads on this subject. Rename me Street Gangs in Europe and make me drop loose change if old.

this guys voice is so hypnotic.

This is actually a topic I'm quite interested in. Thanks for posting this!

Wow I literally just posted about the game in another thread. Exciting stuff! I'll check it out.