TTX Railgon Gondola

A bit of a reporting marks mystery - I missed the full reporting mark and car number in this photo. According to this comprehensive history of TTX reporting marks: www.nakina.net/other/report/reportttx.html , the reporting mark should be GONX. Yet clearly the last two letters of the mark are TX. Can anyone help?

Hasselblad 500 EL/M, Carl Zeiss C T* Planar 2.8/80, Long expired Kodak Vericolor III ISO 400 120 roll film