Any waviness, inconsistency in the seal width, or signs of adhesive residue are red flags
Here's the little snowman with his arms folded over in the front to look like he is hugging the card
Not sure what your budget is, but other handy lands include Reflecting Pool, Field of the Dead (if you can swap out some lands for snow lands), Mana Confluence, Temple of the False God, the Fetches on-color (or even Prismatic Vista or Fabled Passage if you're basic-heavy)
Therefore, I realize that there are certainly places I could improve my code
PSA often heavily relies on enthusiast of the hobby and the knowledge they have acquired on their own
A general rule that can be used to determine the rarity is based on the rarity symbol on the cards