Steam Roster

0-4-0 "Shifter"

B30

The PRR's original locomotive classification system was in force between 1867 and 1895. Under this system, each significant locomotive type was assigned a different class letter even if the wheel arrangements were the same. To illustrate this, classes A, B and C were all 4-4-0 type locomotives but with differing specifications. By the early 1890s nearly every letter of the alphabet had been assigned and locomotives with quite different specifications were being lumped together in a single class. A good example of this is class P. There were a number of experimental and other odd-lot engines, some acquired with purchased railroads, that were not assigned into classes under the old system. It was clearly necessary to change to a new locomotive classification system.
Under the new system, which was used from 1895 until the end of steam, each wheel arrangement received a letter identifier and significant variations between locomotives of like wheel arrangement were assigned different numeric identifiers. The letter A was assigned to locomotives of the 0-4-0 wheel arrangement, with the oldest major variation of this type being identified as Class A1 and the next as Class A2. A small letter 's' indicated that the class was equipped with superheaters (this was done between about 1905 and 1923, after which superheaters were standard equipment on all new classes).