This one's the Model 1909 Bolo, made by both Springfield Armory in 1909 and by Fayette R. Plumb in 1917.
The various European knifemakers saw a ready market in the United States for big. fearsome knives - thanks in part to television and movies showing them being carried and fought with.
They tailored their production after Hollywood's sense of 'artistic license'.
This one's not a 'fighting knife' - it's a brush-clearing and minor utility knife for tropical environments from an era when we were in the Philippines and Latin America.
Insofar as this one's concerned - that little hole is designed so that the Bolo doesn't shift position or rattle in the scabbard - the later, follow-on Model 1917 actually used a lock like that in use on the bayonet - though the M1917CT did not.
Now, if it 'says' 'U.S. ARMY' on the blade - it should also say 'HOSPITAL CORPS' above that, in an etched panel.
If so - it's a Model 1887 Hospital Corps Knife - used for the same purposes as above.
They feature what's best described as a 'spearpoint' blade, with a turned handle..
They 'do' make fakes of this one - beware of old men with a lot of 'stuff' to sell...
Vaya,
Scouts Out!