A word of caution from a qualified geologist.
Recently there has been an increase in people selling pyritic or marcasite nodules as rare Yorkshire coast fossil eggs and or Dorset dino poo, coprolites. There are no know dinosaurs that could hold their breath under water and dive to lay eggs when the Yorkshire and Dorset Coast rocks were deposited. Most of this strata is deep water marine sediments. Saurians ( sea dwelling dinosaurs) gave birth to live young. Within the strata of these deposits you findpyritic nodulebeds.
This is not an indication that there was a sudden mass case of dino- diarrhea but are natural formed pyritic or marcasite bands. The only poo is geing from the content of the sellers description
Currently at time of writing this review there were 68 UK listings. Dont be fooled and end up with a lump of pyrite which over time unless treated will decay.