B17 4-6-0 No 2800 Sandringham when new in December 1928.
I suspect this is at the North British Loco Company Hyde Park Works in Glasgow before delivery.

Alistair B Moffat says "Could be North British Queens Park Works, the former Dubs part of the group near Polmadie on the South side of Glasgow. The wall with its inset panels suggests this as a possibility to me, but only a possibility.
The locomotive works plate however, beside the Westinghouse pump on the smokebox would confirm your own suggestion. The Hyde Park works used the round plate rather than the the far more familiar NB Loco Diamond shape used by the company".

Photo: Rail Archive Stephenson