[Toby Purcell]

Super photo. I think he is a Troop Sergeant Major (and so dressed as 2nd Class Staff) of the 10th PWO Royal Hussars C1870. According to the MHS special publication of 1997 by Linaker and Dine, which is profusely illustrated in its coverage of cavalry insignia, the following badges applied from the 1850s until the changes of 1881:

“in the 1850s [cavalry] RSMs and QMSs started to invert and wear their 4-chevrons on the forearm to distinguish them from TSMs who also wore a crown and 4-chevrons in some regiments”.
NB. This also included the 2nd Class Staff entitled to dress as 1st class.

Examination of period stable jacket patterns shows that the trefoil loop cuff lace, lace outlined pockets, and hook and eye fronts were a feature adopted by the staff of the 10th Hussars after 1860. First Class staff had a double line of narrow lace decoration in place of the single line worn by Second Class staff that’s seen in this case. Ranks below staff wore buttoned stable jackets with a simple lace loop on the cuff. The very low collar is typical of the decade before the 1880s. PoW feathers arm badges were originally in embroidered bullion wire, but from 1869 on became white metal on full dress, whilst remaining embroidered on undress for some time. With regiments geographically widely dispersed in garrisons there was of course a transition period. The enclosed photo shows regimental NCOs in stable jackets, other undress, and atila tunics at Ipswich in 1861. At that time the regiment was still following its original policy of wearing the arm badge above all components of badges of rank, including crowns. That practice had ended by 1869.

Footnote: The other two regiments that wore PoW plumes arm badges, the 3rd Dragoon Guards and the 12th Royal Lancers, had a different style of lace decoration to their stable jackets.