Hi and welcome to the forum.
Probably the best advice is just figure ALL packs/blisters have either been weighed or resealed. Don’t waste your money;) This is especially true if they’re 1st Ed Blisters.
I had a set of unlimited base blisters. Opened the Blastoise art that weighed 34.10 grams, while venusaur weighed 33.62 and zard 33.45. Blastoise pack did not contain a holo unfortunately. Small sample size
Thankyou everybody for your replies. I’ve agreed with the seller that I can inspect the blister and if there’s even the slightest thing wrong I can pull out.