I have a 5" nickel 27-nothing (BTW, as for date of manufacture the plain 27s were made from 1957 to 1961 then the 27-1 was made for about one year before the 27-2s came out) that I bought from a gun shop about 18 months ago for $299. I thought that was a good price to buy. If I were selling your gun I would put it on one of the auction sites starting at $450. May or may not sell but you'll find out.
Oh, can't tell from dark pics, does gun have "diamond" grips? Diamond N frame targets are worth about $200 all by themselves. If they are, I would ask at least $500 for this gun. Or put newer grips on and sell old ones separately.