About 15 years ago I purchased a water-cooled Maxim machine gun with its original tripod mount. It's an ex-Russian gun that was captured by the Finns in the Winter War, and refurbished in their armory, but then sold as surplus. It is in 7.62x54R and it's in excellent condition except the right sideplate was removed to make it BATF legal. My question is, can this gun be legally restored to working condition? If so, who could do the work, and when completed can the gun be returned to me?