How to know used Galaxy Tab 3 is AT&T compatible?

[AC Question]

My apologies if this is a ridiculous question - looking to buy a used tablet for mom-in-law's 88th birthday so that she can try out Facebook and see all her grandchildren and great-grand's pictures, etc. We will let her use data from our AT&T sharing plan rather than commit to internet service. Found a great buy on a used 4G Samsung Galaxy Tab 3 at the local pawn shop, but no box or owner's manual. Is there a way to tell from the model number or serial number whether it's compatible with AT&T? I don't want to buy it and find out it is from Verizon or Sprint. Thank you!

 

[UJ95x]

Welcome to AC
You can look for the model number, and then do a Google search for that. They are carrier specific, so you can see if it's an AT&T version.