These are two titles published by Dainihon Kaiga in Japan, with confusingly similar names. The first, It's Thunderbird Century Modeling Manual was published in 1988; the second, It's Thunderbirds' Century Perfect Modeling Manual was a revised version with reworked art and photos in 1990. Both are large format books with glossy pages; the second has a hard-cover.
This "Panorama Mecha Graffiti" art page is identical in both editions, and shows the design inspirations for the Eagle- the Sikorsky S-64 Skycrane and the Russian equivalent, the Mil Mi-10 (called Harke by Nato). It also includes the Apollo Lunar Module, the Moonhopper (from UFO and Captain Scarlet), and the Eagle picking passenger modules like Thunderbird 2.
The double-page spread from the 1988 book (p108-9) and the gatefold from the 1990 book (p112). Both art by Hideki Kakinuma. Most Eagle and Earth-ship variants, a few alien ships, and the oddly named "moon bagy".
Close up of the 1990 gatefold and reverse.
In the 1988 book, models by Hiroki Yamada, Akihitol Wase and a scratch-build Eagle by Telu Yamada,
Teru Yamada 1999 World, p86-87 of the 1988 book.
Photos of Teru Yamada Eagle variations, and notes on the Hawk.
The Eagle blueprints from p118 of the 1990 book, unusually selecting the Eagle 3 model.