J.G. Brill Co. of Philadelphia, Pa., between 1911 and 1913. The Frankford Elevated portion opened in 1922 along with another set of cars, numbered 501–600, also built by Brill that year, later receiving the designation Class A-15. The two rail lines were soon merged, resulting in a combined fleet of 315 cars (215 Market Street cars, 100 Frankford cars). By 1960, when the PTC began replacing the cars, the Market Street cars had been in operation for 56 years, thus having the longest lifespan of any Philadelphia subway cars, surpassing that of the original Broad Street subway fleet, which had 54 years of operation. The Frankford cars phased out at 38 years of operation. After retirement, two of the "Market" cars (cars 69 and 163) and six of the "Frankford" cars - cars 532, 551, 559, 583, 585, and 589 - were retained as work train cars for some time. It is currently unknown when these cars were withdrawn, but all had been removed from SEPTA property by the 1970s, with none reported to have been saved for museums. The "Market" and "Frankford" cars were replaced by a fleet of 270 new stainless steel cars built in 1960 by the Budd Company. The PTC had designated Class A-49 cars numbered 601–646 as Class A-49, and numbers 701–924 as A-50 and A-51. All cars were re-designated as Class M-3 when SEPTA assumed operation of the line. The cars had been nicknamed "Almond Joys" by many riders as their distinctive ventilation fan housings resembled the almonds atop the Peter Paul (now Hershey's) Almond Joy bar. These cars, while mostly an improvement in quality compared to their predecessors, had been plagued with faulty wheel frame assemblies, causing the body to shake, sometimes violently, as the car moved. The cars' fan housings had provisions for air conditioning units, however, only one car, number 614, had ever been air conditioned, which the transit authority had found to be uneconomical at the time. The M-3 cars also have an export rolling stock for Japan, becoming the . Early in their service lives, some M-3 cars had fareboxes by their center side doors; these were necessary for collecting fares during the hours after midnight, when SEPTA closed cashier's booths at many stations during the era of 24-hour rapid transit service. "Night Owl" service (midnight–5:00 AM) trains operated on a twenty-minute headway (interval between trains) at that time.