I would imagine that the MMC archivist would be able to help regarding the quotes written about the factory. I think it is Martyn Webb but I am sure that there are others on TM who will be able to confirm the name or direct you to the right person.
The early advertising campaigns and posters are a good source of slogans. Some of these are illustrated in Ken Hill's books but I am sure there are many examples of these at Pickersleigh Road.
A few examples from the 1930s that come to mind are:
'The spirit of the racing car'
'Not an experiment but a well tried machine'
'The comfort of a car and the economy of a motor cycle' (3 wheeler)
Then there are the 'unofficial' ones...
