The first twelve NB class sheep trucks (546-557) entered traffic on the W.A.G.R. in 1893. They were followed by another batch of twenty-six in 1896 (212-2146). A final batch of twelve (3001-3012) was built by the Midland Railway Carriage and Wagon Co and entered traffic in 1897. These last twelve wagons had only two brake shoes per bogie rather than the four on the earlier wagons. All of the wagons were reclassified S in 1900.

S2002 and S2127 at Northam in 1907 - blown up from State Library of WA 5323B/1646

At some later point in the life of the wagons the single large doors on the centre line were replaced with pairs of smaller ones on twenty wagons (confirmed for 547, 2122). The WAGR outline diagram of the S class wagons as modified is shown below.

Disposal of the class was as follows:
1948	555, 2141, 2145 written off
1949	556 written off 2125, 2127, 2133, 2134, 2139, 2140, 2142, 3002, 3008 to JETTY 714, 682, 704, 701, 710, 683, 707, 702, 703 Written off 555, 2141, 2145 to JETTY 689, 700, 688
1950	2121, 2126, 2131, 2143, 3005 written off 2130 to JETTY 783
1953	553, 2144, 3006 written off
1954	546, 548, 551, 552, 554, 2129, 2132, 2135, 2146, 3001, 3003, 3007, 3009, 3011 written off
1955	547, 2122, 2123, 2124, 2137, 3004, 3010 written off
1957	2136, 3012 written off
1958	549, 557 written off
1960	550, 2128, 2138 to JETTY 278, 282, 280