The approximate age and value on a 38-40 Winchester model 1873 serial number 259xxxB in good condition?

your model 1873 Winchester was made in 1888,any Winchester 1873 has quite a bit of value,that being said it should vary according to the amont of blueing on the barrel,the barrel inside condition(any pitting),wood finish left on the wood,any cracks in the stock(forearm and buttstock)?You may get a value on this if you have a book by s p fjestad.It is called the blue book of gun values.