Nice Groat. I have a Rosette mascle / Annulet reverse mule. Muling was fairly common on Henry VI groats.
Not seen one of these mules though , extraordinary to think that the Pinecone mascle issue did not start until 1430 and the Annulet ended 1427 , i wonder if they had a large stockpile of those reverse dies.
There's a great book on medieval groats by the late Ivan Buck. There is extracts from it here on Mike Vospers website.
http://www.vosper4coins.co.uk/ivanbuck/Buck-3.htm