The mark 5E denotes your gun as a Grade 5 with the factory auto-ejector option. This is one of Hunters high grade guns and retailed in the $200 range back in 1899-1900 when it would have been manufactured. This gun has fluid steel barrels and should be very shootable with period correct loads; but after being hidden in a leather case for nearly 60 years it most likely needs a thorough inspection and cleaning. You have been given a very nice and high quality gun to enjoy so treat it with the proper care and respect it deserves; as they certainly don't make these things anymore!