2016 Canada $20 Superman vs. Batman 1/4 oz .9999 Silver Coin - Gem in Sealed Flip w/ COA PF-18/Cr. 436 and one-half dollar clad coins

and one-half dollar clad coins will have a shape such that the obverse is concave and the reverse is convex

From the Wikipedia Page on Willy Ley:

Inscriptions are “UNITED STATES OF AMERICA

2012 500 Yuan 1 oz Gold Panda - Gem Uncirculated in Mint Plastic

These notes are sold as "type" and thus the series may vary from 1928

2016 Canada $20 Superman vs. Batman 1/4 oz .9999 Silver Coin - Gem in Sealed Flip w/ COA PF-18/Cr. 436 and one-half dollar clad coinsIn original flip with all Certificates of Authenticity. Mintage 300,000 Composition 99. 99% pure silver Finish specimen Weight (g) 7. 96 Diameter (mm) 27 Edge serrated Certificate not serialized Face value 20 dollars Artist DC Comics (reverse), Susanna Blunt (obverse)