Chris-bob:
Your .38 Military & Police (postwar) was manufactured between 1954 & 1956. Serial range for those years was C277555 to C402923, so 1955 seems likely.
In 1957 the .38 Military & Police was designated the Model 10. N & 42799 are assembly numbers, used to track parts in the factory. They have no meaning after the gun is assembled.
Trader Ray:
Your friend has a Model 37 Chiefs Special Airweight that was manufactured in 1976 or 1977. Serial range for those years was J370001 to J670000, so late 76 would be my guess. The finish is nickel. Stick to standard velocity ammo for practice, the Model 37 was not rated for PlusP until 1997.