The Smith & Wesson Model 28 was a six shot, double action revolver produced from 1954 to 1986 in response to pressure from police forces for a cheap .357 Magnum revolver. By virtue of the Model 28's use by police forces it is also named the "Highway Patrolman", and became a relatively popular Smith & Wesson firearm.
The Model 28 was based on the top-of-the-line Smith & Wesson Model 27, which was a highly desireable (and therefore very expensive) revolver, and one of the few at the time that fired the .357 Magnum cartridge. Smith & Wesson therefore used the basic mechanics of the Model 27 in a less expensive form to produce the Model 28. Unlike the Model 27 (which used a 3 dot, adjustable rear sight) the Model 28 used an adjustable rear sight combined with Baughman front sight.
The major difference between the two was a change in the finishing process, with the Model 28 being bead blasted to achieve a matte like finish and not polished, reducing the cost without affecting its capability. There were also subtle changes in the main manufacturing process, further reducing the cost. All standard examples of the Model 28 have a blued finish.
The Model 28 is an N-frame revolver, up until recently Smith & Wesson's heaviest frame. The heavy frame meant that the recoil produced by the .357 Magnum round was all but negated, and meant that the same frame would be used on the later Model 29 revolver, which fired the .44 Magnum round. The frame itself had been originally designed in the 1930's in the guise of the 'Registered Magnum' the basis of the Model 27.
The Model 28 was one of the few revolvers that fired the .357 Magnum cartridge (which was almost exclusive to Smith & Wesson anyway) which was fired from a six-shot cylinder. The Model 28 was also capable of firing the .38 Special.
The "Highway Patrolman" as it was named was intentionally designed for police forces, and saw steady sales during its production life. Yet it was also popular (if not more so) in the civilian market, being particularly favoured by target shooters who favoured the Model 28's low amount of recoil produced when it was shot. The large frame also meant that users could use more powerful/tuned up versions of the .357 Magnum.
Various police forces used the Model 28, with several requesting special features to be added to the finishing process. One such example was an order by the Florida Highway Patrol which were nickle plated and stamped F.H.P. (these were also given a 5in barrel) with 25 examples being purchased.