I look for three things when I purchase a vintage tin box:
The design is of course the first thing that determines whether or not I want a tin box in my collection. My only criteria is- do I like it or not.
Can I remove the lid?
I never buy a tin box without testing whether or not the lid comes off. Sometimes the lid will have rusted shut - or be REALLY hard to get off. It would be like buying one shoe. It may be pretty but the functionality has completely gone.
I never buy tin boxes or cans that have a bad odor. Coffee and tea smells are okay - as is a smell of sweetness from the home baked cookies they once contained. Other than that - no thank you. Although decorative I want to be able to use the tins boxes as the containers they are.