Big box of baseball cards well over 1000 cards

My grandpa had passed away and had these old cards he had told me that there were many valuable cards I haven’t went through hardly any of them jus scummed through and found very many around 200-250 but he said there are many valuables. They are all pretty much in good shape been stored and put away. This is essentially a mystery box. Willing to negotiate. Bought the cards as a mystery box and found the expensive ones and put them back in the box to save.