Sadly yes, need to be on your toes when dealing with watches. Read and read the reviews on the shop. If its a current model of a watch, get a feel of it an a local authorised dealer. Play around with the watch. Wound it up see how the movement feels. Then go to the watch dealer that you browsed and play with the watch again. See if anything is off. Alternatively i think some watch shop are able to do an authenticate for a fee.