Lets see a 1964 Colt SP1 all original. So what your saying is that you have a rifle with.
1. A carbon steel gas tube, prone to corrosion
2. A bolt that does meet current hardness standards
3. The old bolt catch and spring which stressed the lower receiver
4. The defective Edgewood buffer.
5. An non-chromed chamber and bore
6. No drain hole in the stock retaining screw
7. The old firing pin, prone to slam fires
Not mention all the product improvement made to the A1 and A2 series guns that aren’t on this model.
I’m not sure what these sell for now, but you can see it would take hundreds of dollars to get it up to modern standards.