[quote=@Vongola_Hasayo]
I don't know if you could make the Penny prototype concept work (if we're keeping with canon which I'm assuming since [@EmzyOfNeverland] said this would take place between Volume 2 and 3) since Penny is essentially Penny 1.0. She states that she is the first synthetic person capable of generating an aura ie the first successful attempt.
[/quote]

True, but that does still leave us some wiggle room, as that's (a) only as far as she [i]knows[/i] (given Robodaddy's procilivity towards keeping secrets, it's possible Penny may have just been kept in the dark about any prototypes) and (b) only an issue if we restrict other Penny models to predecessors only, whereas there may have been simultaneous projects dedicated to serving different purposes, like combat, infiltration, bodyguarding, extreme sports, making toast...