A collection of proposed flags for Finland from the 19th century and early 20th century, up until the adoption of the current flag.

Besides the current version, I like proposals no. 2, 20 and 34 (but the last one is too similar to the Estonian flag).

No 2 is dope

Is there a book that shows this progression for each country?

#16 is the flag of catalonia xD

From https://www.crwflags.com/fotw/Flags/fi!prop2.html.
!wave

42 looks like a cooler version of their current flag

#2, 22, 35.

#11 looking awfully Acadian!