Hello all .... outside 3rd rail entered the scene about 1929 ..., it was considered the "in thing" for the scale world till 39 when 2 rail ( thanks to innovations in the HO and OO world) took the lead. Many established clubs & hobbyist's with outside 3rd rail would retain it for decades . The 2 most prominent remaining outside 3rd rail layouts ..are Bay Side in Brooklyn , NY ...which is currently be dismantled and moved to a new location ...and the old B&O traveling layout which was rebuilt last year and operates during the Christmas season in the Cincinnati terminal station ..now museum. At the recent East Penn traction show one of the portable layouts had outside 3rd for elevated trains . I have outside 3rd as one of my layouts ...track saved from an old layout dating back to the 30's/40's . NMRA set standard for the outside 3rd rail for HO, OO and O scale ... yes it was used on all 3 gauges ..for a short while ...
Cheers Carey 
