Is the letter indicating your duties, salary, duration of employment, full time/part-time etc. (all the important requirements of a valid reference letter)? You will need to include other documents with that letter i.e. payslips, tax documents, offer letter, business cards for you and the coordinator (from the closed company)etc. This is what i did and i had the letter, which was not on a letterhead, notarized. Even though the letter may not be on a letterhead, please make sure it meets the other requirements.
