If it's in good optical condition then the Dagor is worth a bit, how much is rather variable as some people are prepared to pay silly prices.
Others think Dagor's are over-hyped but the reality is they are good performers for their age, generally regarded as the best availably pre-WWII, easily out performing Zeiss Tessar's, the companies main selling lenses. Coated & post WWII Dagor's are genenerally the most desirable.
A 210mm Dagor has excellent coverage, 12"x10" at f45 although that drops at wider apertures. The Zeiss made Dagor's are rarer,they seem to have used the Goerz design somewhat grudgingly that may increase it's value.
Ian