Some more information about this. The US military tested the Triple Lock in 1907, but these guns were chambered for a cartridge similar to the .45 Schofield, not the .44 Special. They were probably manufactured in 1906, since the tests started in January 1907. These were definitely prototypes, since they were not commercially available.

There are some on this forum who have considerable expertise on this subject and may even own some of the Army test revolvers, so maybe they will comment on this subject.