As you seem to have figured out, that gun was originally (likely) a model 1892 that was refurbished and had the lock updated. Once done it was remarked on the butt as a "Model 1901". All of this series of guns had consecutively running serials so assuming that Colt kept the correct serial number, then it should be a pre 1898 made revolver. That would make it an antique. Nice looking Colt!