Dan,
Over the years I have seen one other decal like this on a seat spring display, it could even of been Steve Millers at one of the Massey Expo's when he had a mobile display of seat springs and cast iron Massey related seats.
My memory is not as good as it used to be but I am leaning towards and favouring the darker green background on this decal.
Malcolm.
Just been through my photo's and yes it was the Missouri Expo in 2009, here are some very poor photo's that do not really show you what you want Dan, but it is definitely Steve Miller's display, so well worth you making contact with him.