Thanks for the flashbacks, Mark. Those GM fishbowls were a treat to ride when they were new. And Halifax Transit's first livery, in purple and orange, positively screamed early-70s design.
The 400-series T6H4521 models weren't the first GM fishbowls in Halifax. Those were the TDH4519s acquired by predecessor Nova Scotia Light and Power in 1963. Numbered 301-312, they were repainted for Halifax Transit in 1969 and retained their original numbers. They were the only non-electric transit vehicles NSLP owned (well, since the last horse cars were retired in 1896).

Image credit:
David A, Wyatt, University of Manitoba
The photo above, of NSLP 309 on route 8 Bicentennial, was shot just over two months before the city assumed transit operations. The buildings behind are 1895 and 1889 Granville Street. Miller Bros. was a long-lived (c. 1867) supplier of pianos, organs, sewing machines and phonographs. S.S. Keddy & Sons, barber and beauty supplies -- I find the Glidden Paints sign amusing -- is another venerable business. I don't know when it began but it apparently survives today as Eastern Esthetics at 19 Crane Lake Drive, according to a Facebook post by current owner, Susan Keddy.