Worked check
- Find the longest run of cubes on the reference.
- Note the first branch: left, right, up, or toward you.
- Discard any option whose joints do not match after a turn.
- Only then compare leftover cubes. Speed comes after a clean match.
Skill
You are looking at the same object after it has turned. Connections between unit cubes stay. A mirror image is a different object.
Do not try to spin the whole picture as a texture. Pick one distinctive arm on the reference solid. Count how many cubes long it is, then see which way the branch turns. After a rotation, that arm is still the same length and still attached at the same joint.
If two candidates look alike but one is left-handed, reject it. Foldmetry generates original polycubes so you practice the method, not a leaked item bank.