I would imagine that the regalia didn't change much over the years, so your best bet might be to trace the photographic studio through street and trade directories. I did this with an undated portrait, and got it to within 5 years, settling on the date my ancestor opened his own shop.
I'm afraid I don't know what SP means. I have a photo of regalia with the SP on both the sash and the sleeve cuffs. The awards are:
1. Firstly, the Kangaroo, or initiatory membership
2. Then comes the Certified Primo, C.P., meaning a member who had passed an examination on how to chair and keep a Lodge in proper running order. This cannot be acquired before one year’s membership.
3. The Knight Order of Merit, K.O.M., can be obtained after at least three years as a C.P.
4. Finally, the Roll of Honour Member, R.O.H., can be obtained after five years as a K.O.M.
The letters K and M appear on the apron, so I am surmising this means Knight Order of Merit.