After being replaced in 1959 by the modern buses which became known as new-looks, these wartime and postwar models became the "old-looks." This basic design was produced in a large variety of models of various sizes and window configurations.

The model identification system which GM used with these buses conveyed basic information about the vehicle. For example, a TD-4502 was a Transit bus, Diesel engine, 45-passenger, second model of that size. There was also the TG for Transit Gas and the PG or PD for Parlor car Gas or Diesel. (Intercity buses were known as parlor cars at that time.) As hydraulic transmissions became a popular option in 1948, a third letter, M or H, was added to the model number to indicate either Manual or Hydraulic. Thus the model numbers of the most popular GM transit bus began with the letters TDH.

The Yellow Coach name was retired in 1943 as GM divisions were revised during the wartime haitus in bus production. When production of buses resumed in February 1944, the buses were identified with GM nameplates.

The old-looks came with many variations in length and width. The initial models available in 1940 were 28, 30, 31 and 35 feet in length and 96 inches wide. In later years, the maximum dimensions increased to 40 feet in length and 102 inches wide. One exception was an order of 100 for Chicago Motor Coach which, at 41-1/2 feet, were the longest GM old-looks produced.

The first buses produced had vertical windshields which were found to reflect interior lights into the driver's eyes at night. After December 1940, all buses were produced with windshields that slanted inward at a 24-degree angle, eliminating the nighttime reflections.

An optional Thermo-Matic heating and ventilating system was introduced in November, 1946 adding a raised air scoop just above the destination sign.

The windows of the original design had square frames with a uniform distance between each window. Standee windows were optional. The paired window design, with rounded corners on each pair, appeared in 1948. Suburban models had a different pattern created by joining the regular and standee windows to produce a single, high window, also in the paired style.

All the existing old-look models were discontinued in 1959 when the startling, modern new-looks with the "fishbowl" windshields were introduced. Production of new size small buses, models TDH and TGH-3501 and -3502, with old-look styling continued for nearly ten years after introduction of the new-looks because their simpler suspension systems and mature engineering made them cost-effective for many small transit lines still attempting to operate at a profit. Minor improvements were made such as incorporation of quad headlights. They were replaced in GM's catalog by 33-passenger new-looks in 1969.

The grand total of all styles of GM old-look buses produced from 1940 through 1968, according to GM historian Thomas C. VanDegrift, is 38,091.

Information from the Bus World Encyclopedia of Buses - 1988