This is a Triumphonic Tuba with 3 valves. Serial number is 25xxx.
This instrument was advertised as a non-player on a local trading site.
After a proper clean, degrease and service, it has turned to be quite a player and a particularly nice horn!
It is a huge instrument, likely one of those known as a "Monster" by the workers at the factory.
Record indicate this instrument was manufactured in 1947.