The following disclosure is intended for Skybrary goodness.
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Many of the Hidden Fleet craft were nicknamed by players as virtually no info about them was made public during their introduction (for RP purposes).
Here is a list of the official names of the Hidden Fleet craft:

• Hidden Fleet Circle
• Hidden Fleet Platform
• Hidden Fleet Triangle
• Hidden Fleet Square
• Hidden Fleet Blimp
• Hidden Fleet Ring
• Hidden Fleet Mothership

Each of these appear may appear within the Hidden Fleet Legendary Combats.
Legendary Combats introduced with the Hidden Fleet were:

• Hidden Patrol
• Minefield
• Hidden Fleet
• Lighthouse
• Two Towers
• Hidden Circle
• Hidden Triangle
• Hidden Square
• Hidden Airship
• Hidden Ring
• Hidden Raid
• Mine Storm
• Hidden Storm
• Hidden Carrier

Note that other, non-Hidden Fleet craft may ALSO appear within Hidden Fleet Legendary Combats (such as G01D-F15H).
Some craft introduced around the same time as the Hidden Fleet are not, technically, Hidden Fleet craft (such as Proximity Mine).

Wonderfully confusing, ain't it?

Why shouldn't we consider the proximity mine a Hidden Fleet craft?

The circle, platform, and proximity mine showed up during the Legacy event in 2.3 (along with the combats Hidden Patrol, Hidden Fleet, Two Towers, and Minesweeper); the square, triangle, airship, ring, and lighthouse mine came later (2.5?) and the carriers only appeared during the Hidden War.

Wait a sec, I think you're right, Kalin.
They were introduced separately; I had forgotten that.
I wrote "technically" only because they're not "tagged" as being associated with the Hidden Fleet in the database. Since they were introduced earlier, that totally make sense.
Good call.

I have been upgrading the Official Names in the Wiki to Calvin's list, just because I am finding that the Skybrary is rather inconsistent on this matter. Older names will be preserved as Redirects.