Finland.

White ring with a black three numeric code (on left tibia) and metal ring (on right tarsus).

note 1 : code to be read from bottom to top.

note 2 : used codes 000-999, except 666.

note 3 :

White ring with a three alpha-numeric code, starting letter "C" followed by two numbers (on left tarsus) and metal ring (on right tarsus).

note 1 :

Yellow ring with a black three alpha code (on left leg) and metal ring (on right leg).

note 1 :

Yellow ring with a black three alpha-numeric code.

note 1 : in 2022 used codes are : Wxx, Xxx, Yxx and Zxx into use as well as also alpha-numeric rings starting with letters C and F (A is already in use in another project and letters not used are : B, D and E.
In 2025 theseletters are used : J, K, L, U, V.

used combinations are : 
C / letter / number
C / number / letter
C / number / number
F / letter / number
F / number / letter
F / number / number

note 2 : y = yellow ; x = letter ; n = number.
y- Jxn, y- Jnx, y- Jnn,  y- Kxn, y- Knx, y- Knn, y- Lxn, y- Lnx, y- Lnn, y- Uxn, y- Unx, y- Unn,  y- Vxn, y- Vnx, y- Vnn.

note 3 : 

Red ring with a white two numeric code (on left leg) and metal ring (on right leg).

note 1 :

Dark-blue ring with a yellow two alpha-numeric code (on left leg) and metal ring (on right leg).

note 1 : to be read from the bottom up.

note 2 : a bar is used to separate some of the letters i.e., A|A, |AA, AA|

note 3 : birds ringed in Britain & Ireland, Iceland, Denmark, Finland.

note 4 :

Black neckband with a white three alpha code.

note 1 : these include both GPS-tags and traditional neckbands.

note 2 :

Orange ring with a black two alpha-numeric code (letter/number) (on left leg) and metal ring (on right leg)

note 1 : used letters and numbers are : A, B, C, D, F, G, H, J, K, L, M, P, S, T, V, X, Z and 0, 1, 2, 3, 4, 5, 6, 7, 9

note 2 :

Combination of :
* red ring with a one alpha code (on left tibia).
* red ring (on right tibia).

note 1 : used letters : A, B, C, E, H, J, K, L, M, N, P, S, T, U, V, W, X, Y.

note 2 :

Combination of :
* dark-blue flag with a two alpha code (on left tibia).
* dark-blue ring (on right tibia).

note 1 : used letters for alpha-numeric code : A, C, E, H, J, K, L, M, N, P, T, U, V, X, Y.

note 2 :