Values of guns often depends upon condition, the area you are trying to sell it in,, condition,, other expenses such as FFL fees, shipping etc, condition, the rarity of the particular firearm, condition, tiny details about a model, and condition.
You have mentioned the turn line & the blueing loss.
The RENE price guide lists a few things to consider.
If it's a 1964,,, it MIGHT,, MIGHT be a type of the "transition" guns. That makes a difference.
But even if it is a transition type,, since you mentioned it's a 1964 made gun,, it may not make much of a difference.
In general,, a gun of that vintage would be considered in a condition of 95% or better as a collectable type. And the average price a collector would consider reasonable,, according to the RENE Price Guide would be about $570.00. Now,, with the turn line,, and the blueing loss,, that gun would not be a 95% or better condition gun. Use the NRA grading guide for a more accurate method of determining it's condition.
As such,, without more details,, if a FTF sale is to be considered,, w/o fees & such,,, & w/o anything special about it,, I'd consider it a $500.00 gun.
