Correct me if I'm wrong (imagine that on this board rolleyes ) but you said 'white gums'. Coho have a black gum line with just a little bit of white right at the base of their teeth. Also, they do have some spots on their tails, just typically not many below the midpoint and they are usually fairly round, not elongated. What you have described doesn't sound like a silver to me.

Now an atlantic has NO spots on the tail, small x spots on the upper part of their body, and I believe white gums. The tail is basically squared. Sounds like a better match than a silver to the description.