Agree fire service. The cap badge is NFS/AFS and the buttons are right. Mary is astride a 1930's Raleigh bicycle, she may well have been a messenger, carrying information between the appliances at the scene of the fire and fire service HQ etc. That would put her in her late fifties or early sixties, but don't be deceived, there were some very sprightly elderly ladies about in those days and they were needed!