Until the advent of the less than totally successful Q2 duplex drive freight engines in the mid-1940s, fast freight and general merchandise duties on the Pennsylvania Railroad typically fell to the 301 M-1 and M-1a Mountain types. These 4-8-2s often handled heavy passenger or mail trains as well. No. 6747, shown here in an unattributed photo, belonged to the M-1a group, being a 1930 product of Baldwin Locomotive Works, the PRR's favored builder outside of its own Juniata Shops. These locomotives had 72-inch drivers and 27x30-inch cylinders, and carried 250 p.s.i. of boiler pressure. They developed 64,550 pounds of tractive effort and weighed 390,000 pounds; for other specifications consult the commentary for No. 6919 following. No. 6747's 12-wheel tender has the head breakman's shanty atop the water compartment, a feature common in Pennsylvania Railroad practice.