I thought about that one but the collector number matters a bit.  The Elemental on the physical token I have is 4/4, colorless, with Flying, collector number 003/019.  The one listed in the notes, collector number 010/019, is a 3/1 Red Elemental token.  I don't know if both Elementals exist opposite a soldier; I only have the one.

And now that you mention the art -- the Angel // Elemental token has the correct collector numbers, but the wrong back side art for the Elemental.

Another missing C20 token, this time from the Timeless Wisdom deck.
Side 1:  C20 005/019 Soldier
Side 2:  C20 003/019 Elemental

I am seeing the same thing as scramasax.
The Ruthless Regiment deck came with five tokens that are two-sided as follows:
Side 1:  C20 004/019 Human
Side 2:  C20 019/019 Treasure

The Secret Lair: Beyond the Helvault cards are still missing.

They are all printings of Thalia, Guardian of Thraben numbered 37-40.
https://scryfall.com/card/sld/37/thalia … of-thraben
https://scryfall.com/card/sld/38/thalia … of-thraben
https://scryfall.com/card/sld/39/thalia … of-thraben
https://scryfall.com/card/sld/40/thalia … of-thraben

Also, the Challenger Decks 2020 have some unusual two-sided tokens included.

The Cavalcade Charge deck has:
1x On an Adventure (ELD #20) / On an Adventure (ELD #20)
2x Devil (WAR #12) / Satyr (THB #9)
2x Elemental (M20 #7) / Satyr (THB #9)

The Final Adventure deck has:
1x On an Adventure (ELD #20) / On an Adventure (ELD #20)
1x Emblem: Vraska (GRN #8) / Human (ELD #2)
3x Human (ELD #2) / Human (ELD #2)

The Flash of Ferocity deck has:
1x On an Adventure (ELD #20) / On an Adventure (ELD #20)
4x Wolf (M20 #8) / Wolf (M20 #8)

The Allied Fires deck has:
1x On an Adventure (ELD #20) / Spirit (WAR #1)
1x Servo (WAR #18) / Dragon (WAR #13)
1x Dragon (WAR #13) / Spirit (WAR #1)
2x Servo (WAR #18) / Wizard (WAR #5)