sensitive to the formation of massive, luminous stars, and our small M/L values, together with the work of Wozniak et al. (2003) and Wozniak & Champavert (2006) showing that σ − drops can be caused by massive star formation, strongly suggest that the bulge of NGC 6503 has a star-forming component. Thus, the better comparison may be to the nuclear clusters of Walcher et al. (2005), who find M/L$_{I}$ ratios that generally lie below 1. B89 and BG97 present dynamical models for NGC 6503, and BG97 test the models for bar stability. In both papers, the mass distribution of the disc is given by Eq. 10 with a scalelength of R$_{d}$ = 1 kpc, while the velocity ellipsoid is given by where Σ( R ) is the projected surface density, z$_{d}$ is the scale height of the disc, and A and B are the Oort constants (van der Kruit & Searle 1981). The expression for σ$_{z}$ is obtained for an isolated isothermal disc, while the relationship between σ$_{R}$ and σ$_{φ}$ comes from the epicycle equations. However, the relationship between σ$_{R}$ and σ$_{z}$ is an extrapolation from the observed value in our solar neighbourhood. We return to this assumption in § 7.2. B89 also examined a second model in which Q is held constant throughout the disc (Carlberg & Sellwood 1985). For this model, the radial dispersion obeys Both models yield reasonable fits (the former is slightly better), but cannot reproduce the σ − drop. To reproduce a borderline stable disc where Q = 1 . 7 (Sellwood & Carlberg 1984), B89 finds that the disc M/L must be 1 . 7 ± 0 . 3 in the B − band, which is consistent with our findings. BG97 model the galaxy in more detail and provide stability studies. They adopt the gas rotation curve as the fundamental input to their simulations and assume an isothermal, cored halo profile along with the disc from B89. They vary the disc to halo mass ratio to investigate the stability properties of the galaxy; Q declines slightly from the lowest disc to halo mass ratio to the highest. 24 σ$_{R}$ ∝ ρ κ exp( − R/R$_{d}$ ) ( B ( B − A )) − 1 / $^{2}$. (22) σ$_{z}$ = √ π Σ( R ) z$_{d}$ (19) σ$_{R}$ = σ$_{z}$/ 0 . 6 (20) σ$_{φ}$ = σ$_{R}$ √ B/ ( B − A ) (21) 7. Discussion 7.1. Comparison with earlier work