The unknown one's relief is a bit shallow, but I've never seen it before. It's a commemorative coin for Yuan Shikai's short reign as emperor. The four characters say "Hongxian commemorative dollar." These should be worth as much as the others.
The second one is one of the first western style silver dollars minted in China in China for foreign trade. In that F/VF condition in my Chinese catalog, it has a price of around 90,000 RMB or around $14.3k
The third one is a mid-reign 1906 Guangxu silver dollar. In Fine, worth around 28000RMB or $4.4k
However not to rain on your parade, can you check the weights again? The Shanghai tael is supposed to weigh around 36.8-37.0 grams, and the Guangxu dollar around 37.5 grams. Wear shouldn't be able to take a few grams off the coins...
The best way is to weigh the coins and look for subtle details like fine lines on the shield in the Shanghai tael. However with fakes getting so good these days, weighing might not even help...
However for yours, the colors and details look right except the Hongxian commemorative. You definitely have a rare one with the Shanghai tael.
And

to the community! I think you can also try to re-calibrate your scale. A loonie is around 7 grams I think...