SwiftJ1910.2-0546 is a Galactic X-ray transient discovered during a bright outburst in 2012. We use time-series optical photometry and spectroscopy to estimate the orbital period, characterise the donor star, determine the interstellar extinction, distance, and system geometry, and constrain the component masses. Multi-site r-band and clear-filter light curves and WHT/ACAM spectra from the 2012 outburst are combined with time-series spectroscopy from GTC/OSIRIS and VLT/FORS2 in quiescence. Period searches are conducted using generalised Lomb-Scargle, phase-dispersion minimisation, and analysis-of-variance algorithms. Diffuse interstellar bands constrain E(B-V), while empirical correlations involving Hα yield estimates of K2, q, and i. We detect a double-humped modulation with a period of 0.0941 ± 0.0007 d (2.26 ± 0.02 h) during the outburst. Its morphology is consistent with an early superhump, suggesting that the true orbital period may be slightly shorter than 4.52 h. The Hα radial velocity curves do not yield a definitive orbital period. In quiescence, TiO bands indicate an M3-M3.5 donor contributing 70% of the red continuum. Diffuse interstellar bands give E(B-V)=0.60 ± 0.05 and N_H=(3.9 ± 1.3)x10^{21} cm^{-2}, placing the system at a distance of 2.8-4.0 kpc. The Hα line width in quiescence (FWHM_0 = 990 ± 45 km/s), via a FWHM-K_2 calibration, provides an estimate of K_2, while its double-peaked profile gives q and i. Adopting the resulting K_2=230 ± 17 km/s and q=0.032 ± 0.010, and two orbital period scenarios (2.25 and 4.50 h), Monte Carlo sampling returns a compact object mass M_1=8-11 M_sun and an inclination i=13-18 deg for plausible donor masses (M_2=0.25-0.35 M_sun). We favour an orbital period of 4.5 h. Further phase-resolved spectroscopy and photometry during quiescence are needed to better determine its fundamental parameters.