When researching your stocks for
investment value, you can check if the company is still listed.
These exchanges cover the majority of US company securities.
The links may not give you much information beyond the listing
itself but stock certificate research can be narrowed by knowing
which exchange was used or how the company was traded.
Please remember, in today's markets, the overwhelming amount of
trading is done electronically and stock certificates are rarely
handled due to the administrative costs.