What are the marks on the bottom of bottles actually called?

I hunt for old bottles and have approximately 600 bottles with many different Company marks and numbers on the bottom of the bottles and jars. Some like Owens-Illinois I recognize but others are new to me. I am interested in finding out what exactly these marks are called. Not logos or copyright marks or trademarks but these "Company" identifying marks must be called, specifically, something I would certainly expect. Does anyone know what they are?