Stuart Davies identifies the location " Nelson & Llancaiach on the Vale of Neath Line. This would have been the call before Taff Merthyr Colliery, the subject of another photograph in the sequence available. I can now add the Tour itinerary as follows:
Cardiff General - Ninian Park - Radyr - Penrhos Junction
Penrhos Junction - Dolomite Works (Walnut Tree West)*
Dolomite Works (Walnut Tree West) - Senghenydd Colliery
Senghenydd Colliery - Aber Junction*
Aber Junction - Taff Merthyr Halt - Dowlais Cae Harris
Dowlais Cae Harris - Ystrad Mynach South Junction
Ystrad Mynach South Junction - Bargoed
Bargoed - Tredegar Junction Lower - Nine Mile Point - Newport High Street

The train was worked throughout by 6643. Details followed by * was where 6643 propelled the train. Interestingly, 6643 was at the time allocated to Llanelly and withdrawn from service the following month.