argue against a bar-induced cusp flattening in this galaxy. The halo mass we find is necessarily limited by the outermost H I data point at 800 $^{′′}$, and so should be regarded as a lower limit. The outer rotation curve is the primary determinant of the halo mass, so we do not expect significant variations in halo masses across the different runs. We find M$_{20}$ ∼ 60 × 10 $^{9}$M ⊙ across all scenarios. For scenario K we obtain a M$_{d}$ = 3 . 2 ± 0 . 2 × 10 $^{9}$M ⊙ and M$_{b}$ = 7 . 0 ± 1 . 4 × 10 $^{7}$M ⊙ . Larger disc masses are obtained for scenario KL, while the bulge mass is much lower for scenario KG. In scenario E, we find M$_{d}$ = 3 . 0 ± 0 . 4 × 10 $^{9}$M ⊙ and M$_{b}$ = 15 ± 2 × 10 $^{7}$M ⊙ . Unsurprisingly, in all cases the halo accounts for > 90% of all the galaxy mass, while the bulge mass is too small to significantly impact the stability of the disc, except in scenario E. Whether or not the bulge masses are consistent with other values found in the literature depends on whether the bulge is interpreted as a nuclear cluster ( § 6.2). M/L ratios for the disc and bulge are shown in Figs. 19 and 20. In order to reproduce the σ − drop, the bulge M/L ratios must be small, as we find in scenarios K, KL and KG, but not E. The first three scenarios show that the bulge M/L is less than 1, while the disc M/L is roughly twice that (for scenario KG, it is an order of magnitude larger). We find the disc M/L$_{R}$ to be 1 . 9 ± 0 . 3 and the bulge M/L$_{R}$ to be 0 . 9 ± 0 . 1 under scenario K. In scenario E, we fixed the disc M/L$_{R}$ to be 0 . 53 M$_{d}$ , yielding a disc M/L$_{R}$ of 1 . 6 ± 0 . 2 while the bulge M/L$_{R}$ is 1 . 2 ± 0 . 1, which, although larger than 1, is still lower than the disc M/L$_{R}$ . Our models assume constant M/L throughout the galaxy disc in the absence of a stellar population gradient. In particular, stellar M/L ratios tend to increase in spiral galaxy centres where redder colours prevail (Bell & de Jong 2001; de Jong & Bell 2007). From B89, B − R across two disc scale lengths for NGC 6503 varies from 1.10 to 1.41, correlating with M/L$_{R}$ ratios of ∼ 1 . 3 − 2 . 7 using Table 3 of Bell & de Jong (2001), which is consistent with our findings. Upper limits to the dynamical M/L$_{R}$ values were obtained by Broeils & Courteau (1997), who find M/L$_{R}$ ≲ 4, also consistent with our values. The M/L values for the bulge do not, by contrast, coincide with other bulge values found in the literature for nearby spiral galaxies. Yoshino & Ichikawa (2008) generally find that their bulge M/L ratios are larger than their disc values with few exceptions; M/L$_{V}$ ratios are ∼ 4 . 5 ± 2 . 4 and M/L$_{I}$ ratios are ∼ 2 . 7 ± 1 . 8. In no case is the bulge M/L$_{V}$ value lower than 1, and only in a few cases does M/L$_{I}$ fall below 1. NGC 6503’s bulge M/L lies significantly below nearly all the bulges in this sample. However, M/L ratios are highly 23 6.4. Masses and M/L ratios