How to check if a table exists in a given schema

Postgres 8.4 and greater databases contain common tables in public schema and company specific tables in company schema.
company schema names always start with 'company' and end with the company number.
So there may be schemas like:

public
company1
company2
company3
...
companynn

An application always works with a single company.
The search_path is specified accordingly in odbc or npgsql connection string, like:

search_path="company3,public"

How would you check if a given table exists in a specified companyn schema?

eg:

select isSpecific('company3','tablenotincompany3schema')

should return false, and

select isSpecific('company3','tableincompany3schema')

should return true.

In any case, the function should check only companyn schema passed, not other schemas.

If a given table exists in both public and the passed schema, the function should return true.
It should work for Postgres 8.4 or later.