Oh, wow! These are great coins, Gloria. Your 1875 US trade dollar has chop marks, and I really like coins with chops. (Note: not all collectors are like me!). Go to this CoinQuest page to get the current catalog values of US trade dollars without chops, then adjust that price for the chops.
The coin in the picture comes from eBay seller AlanHo73, and CoinQuest thanks them for the use of their image. It's a beauty and has plenty of chop marks.
So here's the story. Trade dollars were issued by the US government for use outside the country, where local coinage was unavailable or unreliable. Trade dollars used in Asia often show chop marks. These are small, punched-in marks in the coin put there by merchants. A chop mark roughly means 'I, the merchant, accept this coin at full value and give it my seal of approval. You can use this coin in my shop anytime.'
In my opinion chop marks add plenty of interest to already interesting coins.
Sometimes these coins sell for more than catalog value because some collectors (like me) seek out coins with chop marks. On balance, some collectors do not like chop marks and will never buy them. Go to eBay and search for 'trade dollar chop' and you will see the great variation. In general, chop marks have no overall affect on the value of a coin, because the collectors who like chop marks are balanced by the ones who do not like chop marks. If you can fin a collector who likes them, he or she may pay $10 US dollars over a chop-less specimen.