Found something sealed?

Do not open it yet.

You do not need to decide whether it is valuable. You only need to avoid destroying information before you identify it.

The first ten minutes matter

Do not remove price stickers, tape or labels. They may help establish age, retailer, provenance or packaging state.
Do not add your own shrink wrap or tape. Preservation is not restoration.
Do not scrub, solvent-clean or polish the package. Surface dirt is preferable to irreversible damage.
Do not power on sealed electronics by opening them. Document battery and chemical risks instead.
Photograph the item where you found it. Front, back, sides, seams, codes, stickers and damage.
Write down what you know about its history. Who owned it, where it was stored, receipts, old photos and case provenance.
Identify the exact edition before checking value. Similar-looking packages can be different markets.
Use sold transactions, not wishful asking prices. A listing is evidence of an ask, not a sale.

If the item is wet, moldy, chemically leaking, swollen, hot, corroded or otherwise hazardous, prioritize safety and appropriate professional handling over collectible value.

Then do this

Build an identification worksheet.
Create a Case File.
Run direct-match sold research.
Document package condition and seal evidence.
Only then decide whether opening, grading, selling or preserving makes sense.