1995 omanyte pokemon card value | 1999 FOSSIL You cant add more than 20 damage in this way. Dark Omanyte [1st Edition] #37

Ditto Serum Visions, which might be underpriced as a $3 uncommon

The Beckett online price guide features pricing checklists for over 11 million sports and non-sports cards, as well as organization tools for appraising your own collection, a mobile app, and six free graded card submissions with a one year Total Access subscription

Theres three variants, plus the usual Extended Art treatment

Note that both are instant speed, so you can make a token when someone attacks you and block, or EOT your foe's turn to double and then untap and swing with your newly made horde

EDIT: A new and more likely theory has presented itself for Grey stamps in this post by @pokemonrevolution

The range of options for building around prowess is truly as open as the range of non-creature spells that can enable it