So far, since BeeSee reminded us of his article in the Corgi Times, I've identified 32 different varieties.
I will gladly assist BeeSee with a publication.
Obviously some may not be constant, such as Pane 1 Position 1 with the additional "string on the roof" or others where the "variety" is in a different position from that previously identified.
Pane 1 Position 02 - Black dot under "r" of "painter"
Pane 1 Position 02 - Black dot under "r" of "painter" & String on the roof
Pane 1 Position 03 - Black dot in upper right corner
Pane 1 Position 05 - Black dot below man at shop
Pane 1 Position 14 - Black dot below man at shop
Pane 1 Position 16 - Blue dot above horse and Black dot left of "painter
Pane 1 Position 19 - Pink sun in sky
Pane 1 Position 22 - Black hole in roof
Pane 1 Position 28 - Rock in snow below red sleigh
Pane 1 Position 30 - Faint string in lower right corner
Pane 1 Position 31 - Black stick in snow under blue sleigh
Pane 1 Position 37 - Black dot in lower left corner
Pane 1 Position 38 - Red dot in snow
Pane 1 Position 39 - Black bird left of chimney
Pane 1 Position 44 - Black dot between man and horse
Pane 1 Position 48 - Blue bird in sky
Pane 2 Position 01 - Rock in snow below fence
Pane 2 Position 27 - Red line on roof
Pane 2 Position 32 - Dot above sleigh driver
Pane 2 Position 45 - Blue hole in roof
Pane 2 Position 50 - Hole in roof
Pane 3 Position 32 - Accent on "U" of "CORNELIUS"
Pane 3 Position 32 - Broken sleigh, red mark to right
Pane 3 Position 45 - Blue hole in roof
Pane 4 Position 07 - Dot left of middle fence
Pane 4 Position 14 - Black dot in margin to right of shop
Pane 4 Position 15 - Dot above NA
Pane 4 Position 16 - Black dot on wall of shop above the horse
Pane ? Position ?? - Green sky tint (sunrise)
Pane ? Position ?? - Hickie on "D" of "CANADA"
Pane ? Position ?? - Doubled dog" due to green colour shift
Pane ? Position ?? - Strong red line between the two tallest trees
Pane All Position Column 4 - "Broken door frame on shed"
I have a complete pane 2 and most of a pane 1 as well as other singles.
I'm missing:
Pane 1 Position 05 - Black dot below man at shop
(I must have given it away long ago, before I knew of it)
and these two which I've seen somewhere on a forum:
Pane ? Position ?? - Green sky tint (sunrise)
Pane ? Position ?? - Strong red line between the two tallest trees
and
all Pane 3 and 4 varieties.
Many of the varieties, such as the blue and red "dots" are due to colour shifts.
Here's an extreme example:
