Must have been the ever popular Model TR-6.
KRAMER: Uh, well, there's someone else.
OLIVE: Someone else?
KRAMER: Yeah, yeah, yeah...
OLIVE: Who is she?
KRAMER: Her. (he points to the Elaine mannequin in Jerry's car)
OLIVE: her?
KRAMER: Yeah, there she is. That's my gal.
OLIVE: You're a liar. I've seen her in here before. She's not your girlfriend.
KRAMER: Now Olive, look, I'm sorry.
OLIVE: Why is she wearing her underwear?