John,
That is a very nice stamp I have seen pictures of them before but don't have one in my collection yet, Good find and now you can say you have a Cub in your collection.. As far as Wallis Cubs going to Russia here is a picture of at least one I believe made it there.
Next thing, Have you ever seen or heard of an
Electric Wallis? Here is A picture of one and if it works a link to the story on it. It was very short lived because of the week frame without the engine being mounted in it to keep it from twisting. I like how they took the front steering mechanism off and mounted it on the right side of the tractor, never seen that before.
Click link below.
http://www.guardianonline.co.nz/heritage/electric-tractors-were-short-lived/
Joe