Keith, Pyroxylee denotes nitrocellulose, i.e. smokeless. It is seen stamped on French barrels as 'Poudre Pyroxylee' to denote that the firearm is proofed for nitro. We British stamp NP for Nitro Proof. The info I gave is from the Google search on T and T- bis where it specifically gives 'Nitrocellulose' against these powders. Same word as in English.
Late 19th, early 20th century was a time of rapid development of the still relatively new smokeless powders. Many different concoctions were produced. Each with its Trade Name. With some intended to substitute for BP in BP proofed arms. Most disappeared as quickly as they appeared. T-bis was perhaps one of those?
Very attractive bottle. If I had it I would have it on my shelf on display. A bit of history.
Regards,
Peter.