375whelenIMP,
If it is US made, the cartridge is more likely 25 Krag( 30-40 Krag, necked to 25 caliber, maybe improved) than 6.5x55. You should be able to tell which by checking if bolt face is for rimmed(25 Krag) or rimless(6.5x55) cartridge and "slugging" the barrel(.257" grooves, 25Krag: or .264-.265" grooves, 6.5x55).
Mike