How can there be a one Nirvash, not to mention two? At the end of the original series (Psalm of the Planets Eureka Seven), 


   Nirvash left with some Scub Coral to prevent the Limit of Questions, so there shouldn't even be a Nirvash. 


In the sequel, Eureka Seven Astral Ocean, both Renton and Eureka have one.
It's mentioned in Eureka Seven AO that this Nirvash (RA272, Mark I) was originally created by Renton (as a homage to the original Nirvash from Eureka Seven, "typeZERO.") for Eureka in the far future, and was named "Nirvash Neo." 

This new Nirvash does not initially have an Archetype.