Z19 Class 0-6-0 (pre 1924 A93 class)
These diminutive locos survived into the early seventies, working on shunting duties in the major yards. They also saw service on steeply graded and tightly curved lines, due to their short wheelbase. A 19 class was the first NSWGR steam locomotive that I ever saw. The occasion was in August 1970, when, while on my way to the theatre (to see Hair), I saw a 19 class shunting on the bridge over Ultimo Road. Unfortunately, it was dark, the engine was dirty, and I couldn't make out the number. I now kick myself that I didn't follow up on that opportunity and start chasing trains in more earnest while they were still in revenue service.
As it is, I only have views of the LHS of the two locos in this gallery.