Railroads generally with exceptions used heavier and newer rails for more important, heavier traveled, and higher speed tracks and main lines, and used lighter, older, and sometimes used rails for secondary tracks and sidings. (New rail often becomes harder on the wearing surface (top) after some use ("work hardening"), so Professional Engineers sometimes advise that tracks that get VERY heavy wear, like on curves with heavy cars, be laid with almost new, barely worn rail from less severely used tracks. Usually, the person in charge of the labor expenses is not willing to do this extra work just to save money for the person in charge of the material expenses. For an additional charge, the steel mill might make the new rail harder than usual.)
Based on my experience with the Reading's New Hope branch, it seems that in the 1st half of the 1900s, the Reading used 130 pound per yard American Railway Engineering Association Head Free Type B rail (130RE-B) for their heaviest lines, like Bethlehem, Cattawissa, Wilmington & Northern, Atlantic City RR, and others. Probably earlier, they had used some 130 pound per yard American Railway Engineering Association Head Free Type A rail (130RE-A) and regular 130 pound per yard American Railway Engineering Association rail (130RE). Lighter service lines, and before this, almost all lines used 90 pound per yard American Society of Civil Engineers rail (90AS or 245 Maryland) or 100 pound per yard Philadelphia & Reading rail (100P&R or 165 Maryland; 100PR is a Pennsylvania Railroad rail) or its newer name, 100 pound per yard Reading Company rail (100RDG or 100RC or 100 RCo). ACSE rails are usually as high as their base is wide, the Philadelphia & Reading's designer made the base and head taller to turn 90AS into his 100P&R rail! Earlier, as far back as the late 1870s, some 85 pound per yard American Society of Civil Engineers rail (85AS) may have been the standard, because some can be found in old sidings. Near the end of its life, the Reading Co. was forced to use more common rails like 131 and 140 pound per yard American Railway Engineering Association rail (131RE and 140RE), as the steel mills wanted more money to roll different rails for each railroad.
"Maryland" must have meant that the number was a catalog number from what was later Bethlehem Steel's Sparrows Point, Md. Mill; Pennsylvania or P.S.Co. was probably later their Steelton, Pa. Mill; Lackawanna Coal & Iron was in Scranton, Pa.; when in Buffalo, N.Y., I think they call themselves Lackawanna Iron & Steel. CC means "Control Cool", any mill will do it for a price. The "1's" after the year tell what month, December, the 12th month of the year has 12 1's!
