I love this! Thanks Pat:
The card has the ‘G. Herring’ trademark in the top corner. This button was advertised during 1937.
In 1937 G. Herring & Co. Ltd were advertising for an agent for overseas buttons and buckles.
This may have been the start of the company’s focus on buttons, at least as an importer. They would also start to make pearl buttons around this time. The butterfly button above is therefore an early example from this company; possibly imported.