Each munitions factory had a munitions workers canteen. It's a matter of identifying the location of this one (the Princess Louise cypher will be key I suspect). Here is another badge (note the explanation):
https://www.flickr.com/photos/23885771@N03/6996356457
For those interested in further reading see here:
http://preserve.lehigh.edu/cgi/viewc...56&context=etd
Because the munition workers themselves were issued with lapel badges recognising their important work it was natural that those who worked in their canteens wanted a badge too. There is a good image showing the size of these canteens here:
http://www.documentingdissent.org.uk...and-morecambe/