The Fotos TM was the original hard triode produced in France during WWI.
Grammont was the company and Fotos their trade mark. When demand outstripped their capacity another lamp manufacturer, Compagnie Generale des Lamps, became involved, their trade mark was Metal and the valve TM Metal. There are differences in the construction that can help to distinguish the different makes. In particular the Fotos spherical envelope touches the base whereas the Metal made valves have a short stem before the spherical part of the glass. SeeR Type for style.