Class QBL was the final derivative of the bolster wagons dating back to the original class Q of the 1890's. A total of forty of these wagons were created by modifying QBB class bolster wagons in 1973 (1674, 1692, 1713, 1763, 1774, 1776, 11788, 1881, 2220, 2857, 2863, 2900, 2970, 2973, 3297, 3308, 3324, 3378, 3384, 3432, 3437, 3518, 3524, 3544, 3546, 3565, 3569, 3576, 3585, 3588, 3593, 3595, 3598, 3600, 3646, 4669, 4769, 4771, 4782, 4826) The final disposal of the class is as below:

1975	2220, 3569 written off
1976	2863, 3324, 3524 written off
1977	1881, 3384, 3437, 4826 written off
1978	1674, 1763, 2973, 3308, 3432, 3518, 3588 written off
1979	1713, 2900, 3297, 3378, 3544, 3565, 4769, 4771 written off
1980	3595, 3600, 4669, 4782 written off
1981	4669, 4782 written back
1983	1776, 2970, 3576, 3593, 3598, 3646, 4669 written off
1984	1788 written off
1985	3585 written off
1986	1692 written off
1987	1774 written off
1990	3546, 4782 written off
1991	2857 written off