Airship Guide

[Grimmel]

It's not the SS rank that gave you 2 spoils. It was the Optimal yield.

In previous screenshots where people have only gotten one Iron Voyage Spoil, the Optimal Yield was the same as mine.
If you look at my Screenshot and the one two posts below yours, you can see the optimal yield was the same as mine. The only difference is that theirs was a regular S rating (which I believe is the second best rating), where as mine was a SS rating (the best rating so far). So I do think the rating has something to do with the quantity.

Let me go through the entire log of the previous voyage to see if there were any other conditions noted that could have possibly resulted in the 2 Iron Voyage Spoils being brought back.

[Ilmoran]

In previous screenshots where people have only gotten one Iron Voyage Spoil, the Optimal Yield was the same as mine.
If you look at my Screenshot and the one two posts below yours, you can see the optimal yield was the same as mine. The only difference is that theirs was a regular S rating (which I believe is the second best rating), where as mine was a SS rating (the best rating so far). So I do think the rating has something to do with the quantity.

Let me go through the entire log of the previous voyage to see if there were any other conditions noted that could have possibly resulted in the 2 Iron Voyage Spoils being brought back.

There's also an optimal yield that got 2 Iron Voyage, but only a B rating. It seems like the rating is an average of the yields of the entire voyage (hence your optimal+optimal was SS, the optimal+excellent was S, and the optimal+normal was B), and like there is more than one actual yield possible for "Optimal" extraction.

[Eldelphia]

I think our Mammet is blind. Our ships can't find the new sectors. I guess this is payback for going 1/1 on discovering Diadem...