With additional information kindly supplied by William Snook.

In late 1996 a total of 56 former British Steel Ravenscraig iron-ore tipplers were rebuilt by Marcroft Engineering at Stoke for use by British Steel's Strip Products division carrying steel coil between Shotton and Llanwern. The source wagons were a mixture of inner and outer wagons but all gained conventional drawgear at each end. New numbers BSSP4020-4076 and BSSP4091-4099 were allocated, these following from a fleet of tube wagons withdrawn in 1986 (BSCO4000-4019). The two distinct number batches were reported to be due to coupling differences, BSSP4020-4076 having 'new type drawgear' and BSSP4091-4099 'old type drawgear', although this is not evidenced by the design codes. BSSP4020-4064 plus BSSP4076 and BSSP4091 were all assigned design code JS050A, and were rebuilt from JUA inner wagons, while the remainder were former JTA outer wagons and were given codes JS049A (for wagons BSSP4070-4075/4097-4099, rebuilt from former rotary coupling outers) and JS049B (for wagons BSSP4065-4068/4092-4095 that had been non-rotary coupling outers). The two missing numbers (BSSP4069 and BSSP4096) were coded JS049C and JS049D respectively by 2008, but it is not known if this was from conversion or related to a later modification. All wagons were given TOPS code JSA-A. The steel hood featured angled cove panels and flat tops, and was painted in British Steel blue with the logo and Strip Products lettering on the largest hood section. By 2003 many of the wagons were appearing with silver hoods (new or repainted?), the framing and end panels remaining in blue. At about the same time the TOPS ownership prefix was changed to VTG and the logo of this company was applied in black on the hood sides.

A second batch was converted from late 1997, again by Marcroft Engineering, but with alloy hoods to a very different design. Converted from the PR26801-26850 batch of JTA/JUAs formerly used by ARC, all the source wagons were of the inner type, so new drawgear was fitted at each end. The hoods, which were much lighter than the steel ones fitted to the earlier batch, had curved tops and a distinctive colour scheme of silver with the framing and ends in light green. Apart from the colours, the hoods were very similar to those fitted to the BIA, BWA and BXA conversions from BBAs. Numbers CAIB3063-3080 were assigned to the 18 wagons, these following from an earlier batch of covered steel carriers (PDUF3008-3062). TOPS code was JSA-B and the design code was JS051A. Initial use was carrying imported steel from Boston Docks to Round Oak. It would appear that this design was not so successful, and all were reported withdrawn for disposal by 2011.

In late 2007, a third batch of 40 wagons started appearing from W H Davis. Numbered VTG4100-4139, all were to design code JS050A, even though the source wagons comprised a mixture of inner and outer types. The new wagons were essentially identical to the earlier BSSP conversions and had the silver/metal hoods from new.

Many of the JSA wagons were placed in store in about 2014, while issues with the use and maintenance of the sliding hoods appear to have outweighed the load protection benefits that they offered. A few were returned to service in 2017 but it was decided to rebuild the wagons as open coil carriers.

JSA VTG4094 was the prototype example to be refurbished into an open coil carrier. The wagon departed WH Davis on 24th February 2016 in the consist of 4Z66 Shirebrook - Milford West behind loco 66172. As well as removal of the hoods, the ends were cut down in height and given an opening in the middle to facilitate loading/unloading. The trial was deemed successful and the go-ahead was given for the rest of the fleet to be overhauled in this way.

In 2018, the wagons steadily passed through Arlington Fleet Services at Eastleigh. They were outshopped in black with blue VTG lettering and assigned new codes JSA-C and JS052A. The first five to be outshopped at Eastleigh were VTG4026, 4034, 4037, 4061 and 4133 in May of that year. Work continued into 2019 and eventually covered 86 of the 106 wagons.

The remaining 20 of the fleet were converted to JNA-A bogie box wagons instead, with these conversions taking place at WH Davis, Shirebrook in 2019. Somewhat ironically, these rebuilds looked rather similar to the British Steel tipplers from which the JSA coil carriers had originally been converted! The majority of the work for these JNA conversions is in the south of England at places such as Cliffe, Bramdean, Hoo and Stewart's Lane.