Quote from the NLS site:
The database records the type of index, the dates covered, and the libraries that have a copy. You can search by newspaper title and by keyword. Please note this resource does not offer a complete list of Scottish newspapers, only titles which have been indexed. Currently searching 183 titles.
www.nls.uk/collections/newspapers/indexes/index.cfm (http://www.nls.uk/collections/newspapers/indexes/index.cfm)