This picture from the 1966 Prestige brochure indicates the seat with armrest (they called it the 'profile back bench seat with standing center armrest') was available on Bonnevilles:
http://www.oldcarbrochures.com/stati...estige-13.html
However, if you go to the last couple pages of that brochure it seems to indicate that seat was only available on the Brougham and Grand Prix. So, who knows - the brochures didn't always agree 100% with what was actually available.