I have one of the S1's. I bought it at an live auction as well as several other 3rd rail locomotives.It's a beautiful locomotive and a decent runner so far.Due to it's length,it likes 081 or larger.I also have MTH's and Lionel's versions.They will run on 072.The 3rd rail model has a superior level of detail.The MTH model of the S1 runs the smoothest and the Lionel model has superior sounds.
I have a dozen other 3rd rail steam locomotives.They are great looking models and very fine runners once broken in.Because they are hand crafted brass with tons of added on details,they are delicate and not for everyone.