Is there an easy way to tell if a pan/pot is oven-safe?
Speaking in generalizations, without knowing the details of content:

Anything with a non-stick coating- I wouldn't put it in the oven. If you don't know what the non-stick coating is made of, you can't be sure if it will melt. Additionally high temperatures and non-stick coating make for off-gassing.

Anything with plastic handles, knobs or any other plastic parts- don't put it in the oven at any temperature. No way to know how it will react.

Cast iron- always oven safe to almost any temp that a non-commercial oven would reach

Enameled cast iron (like Le Crueset)- oven safe to 500°F (260°C)

Uncoated stainless steel- oven safe to 500°F (260°C)

Uncoated anodized aluminum- I would say no more than 450°F (230°C), to be safe

Copper- 500°F (260°C)

Glass- 450°F (230°C)