Civil Censorship Study Group

Russian Postal Censorship in Finland - 15 Aug. 1915 to 28 Jan. 1918
https://censor.jiv.dk/

Censorship was performed at 10 offices throughout Finland

listed in the catalog:
Censor stamps
Censor tapes
Wax seals
and Censor signatures

If you can offer updated information, please do not keep it to yourself.

Thank you for that very useful information. It is indeed a well organized, beautifully formatted, and substantial resource!