If the 44 Magnum is a 5-screw and all correct (stocks, case, accessories) I would value it at $3,000. If it is a 4-screw, I would value it at $2,500. If the 44 Magnum actually shipped in 1956, it would be worth more to me because I collect early guns (premium around 15-20 percent).
If I were going to make an offer on it, I would start by offering 80 percent of the above values and be prepared to go up to them.
Bill