Mermaid:
Action
Cost: 3
+1 action
Draw the top and bottom card of your deck
Return one card from your hand to the bottom of your deck
is of course much much stronger than PD, but as it doesn't stack, $3 is probably ok
Pearl:
Treasure
Cost: 5
Worth 2 Coin
During the clean up phase, you may return one pearl to the bottom of your deck instead of discarding it.
Without support, this is next-to-not-better than Silver. At the bottom, it will most likely miss the reshuffle and therefore not get played more often than if it would have gotten discarded. Exceptions: It does not miss the shuffle (probability 1/5 without draw, less with), or it would have missed the next reshuffle if discarded...
$4 would be fair, but Donald said he doesn't like Silvers for $4...
Probably you it would be possible to drop the condition of only returning one to the bottom, than it could be played as a reverse Stack. Ok, def's right, that's overpowered.
Rear Admiral:
Action/Attack
Cost: 4
+1 Card, +1 Coin
Each other player returns cards to the bottom of their deck until they have 3 cards in hand
Ghost Ship, Ghost Ship. So how do they compare? For first, I'll give it +2cards, then it's easier. If I return bad things, the attack seems weaker. I don't see the cards that early, they might miss the reshuffle, that's all great for me. So it's more like Militia. If I decide to return good cards instead (under constant attacks maybe), I can prepare a real good turn at the end (on the danger of them missing the shuffle). Not often, but perhaps sometimes worthwile (Put 2KC and 3 Bridges there...)
Hard to tell, but seems weaker than GS, and not so much stronger than Militia (if at all), $4 might be ok.
Reserves:
Action
Cost: 5
+1 action
Draw up to 10 cards in hand
Return 5 cards to the bottom of your deck
wuwuwu. Don't know. That's of course the killer combo-activator. For this part like an instant-Tactician. But with drawbacks of course, no second action, no buy, put 5 cards back. Seems fair. Biggest problem perhaps that it can easier be played every turn than Tactician. But maybe also its justification.
Scrapper:
Action
Cost: 2
+1 Card
+1 Buy
Return all treasures played this turn to the bottom of your deck
Clustered treasures. I still can't really rate this part of Mandarin. Can be really great, often it really hurts. Don't know...