My son has a .38 special 5 shot,5 " barrel. Serial # is D-23475 Need to know approx. what it is worth.

That serial number comes from 1968 but a model 10 would be a 6 shot, not 5. As for value, condition is everything. What finish? What grips? Do they number to the gun? Does he have the original box and goodies that came with the gun? All this will help with a value.

Let me add, welcome to the forum.