The value of a coins depends on many factors including its country of origin, denomination, condition, mintmarks (if any), errors, etc. Assuming that you have a US silver dollar from 1900, then you have what is known as a Morgan Dollar. Look on the back under the eagle's bottom feathers and you might see a small letter. If there is no letter there or an O then in bad condition your coin is worth about $17 to $20, in good condition it would be worth around $25 and if it looked almost new then it would be worth between $38 and $60, but if it still had all of its original lustre (shinyness) no scratches, and its not worn down at ALL then it would be worth potentially between $1500 and $50,000 depending on numerous factors. Now if it has the small little letter S then in it would be worth potential $23, $50, $200, and $2000 respectively. If you have a rare 0 over CC then it would be worth several hundred dollars at a minimum.
