Groundloop,
My apologies - you're correct it's an ex-BCAL Series 530 according to the museum website. When I saw it a couple of years ago, I was under the impression that it was an ex-Channel aircraft - they had the only 400 Series with twin overwing exits as the IT configuration (99 pax IIRC) demanded it. A test flight (As SLB with the rest of my Apprentice School class) to check the pressurisation systems was the only flight I ever had on a 1-11.
The 1-11 was aimed squarely at the American market. The AUW was at the then maximum allowed with just two crew. The airlines that took them also included United, Aloha & Alleghany. I still have a marketing brochure that details a day's flights for a Braniff aircraft going from Love Field all around Texas and making a profit on every leg even when the number of pax was down to about 30 (the Mail subsidy really covered the expenses).
It's funny, I was reading a press release yesterday for Bombardier's proposed C-Series which said the ideal regional was 5-abreast seating and 110 pax - same as the 500!