These models were first introduced by Walthers back in the 1990's. In 2018, Atlas acquired the tooling for these car (among others) and re-released them as part of their "Master" line in 2019. For whatever reason, Atlas designates the bulkhead cars as being 48' (as opposed to Walthers, who called them 54' cars). I'm assuming the 54' designation is the full car length and the 48' designation is the interior length (between the bulkheads).
As pictured above, these cars are available with or without bulkheads. Here's what Walthers had to say about them -
One of the most common of all flat cars, GSC "Commonwealth" 54' Flat Cars have been in service since the 50s. Built around a large one-piece steel casting, the prototypes could handle a wide range of cargo and were often rebuilt for piggyback loading. In later years, they were fitted with bulkheads and handled loads such as lumber and pipe, and some lines added portable bunks for handling logs. These revised Walthers N Scale freight cars feature finer detailing, paint, graphics and come equipped with Accumate magnetic knuckle couplers. Each includes a clear plastic case that's ideal for storage and transport. The cars come equipped with bulkheads as appropriate for each roadname and they're available individually and in limited-run two-packs for a total of three roadnumbers per roadname.
Here's what Atlas has to say about them -
These models are based on a General Steel Industries 48-foot interior-length prototype introduced in the 1960s.
The flat car has long been a versatile and venerable car in the railroading industry. With four open sides, any commodity could be loaded onto the car without constraints. Starting in the mid-60s, a new group of 53' 6" flatcars were built to accomodate each railroad’s needs. The cars were built with a wood deck, along with stake pockets on the sides of the car. Many of these lasted through the 80's and longer in MOW service fleets.
Atlas Features -
- Die-cast body
- Detailed deck
- Detailed bulkhead lattices
- Ready-to-run
- Superb paint & Lettering