[mint74]

I have a complete set of topps 1990 and 1991 baseball cards. Still in original plastic. Wonder about any valuable cards in each set, and value of set unopened in original plastic.

[djohn]

Those sets were both extremely overproduced. There are a few key cards in each set. 1990 has Frank Thomas rookie, and 1991 has Chipper Jones rookie. However in terms of value, these factory sets can easily be purchased for around $5 a piece, so there really isn't much value for them. In terms of keeping them sealed versus opening them, there really isn't much difference in value simply because they are already so inexpensive. They are fun sets to go through and look back at the players of the era. The 1991 set has some really good photography mixed in, which can make it fun to look through.

[Nintari]

As the poster above me said, they were extremely overproduced so the value isn't going to be there BUT... there are a few cards (again, like the poster of me mentioned) that when graded highly, can fetch some money. For instance, a 1990 Topps Frank Thomas BGS Pristine can bring in hundreds of dollars etc.

Of course, the odds that your Thomas is going to grade that high is highly unlikely, but hey... what do you have to lose? I say open it up and find out what you have.

[mint74]

Thank you for the input. I will go ahead and open them.

[alfredoleal2001]

i would open them up and trying my luck sending the mentioned cards in for grading!!

[djohn]

i would open them up and trying my luck sending the mentioned cards in for grading!!

You might want to be a bit hesitant before doing that. I would bet the average card from a factory set will end up grading around a 9. Go look at the resale values for the key cards graded as a 9 and you will find that it's more expensive to pay for grading then just buy the card already graded. Now if you can land a 9.5 or 10, you can make some money, but there is a reason for that (it's not as easy to get the higher grades, even from a factory set).
If you understand card grading then you will be able to carefully examine the cards to be able to have a good idea as to whether they have a chance at a 9.5 or 10, but it's no guarantee.