Hello Alex,
The 3 lugged OSD's were normal private purchased badges, I have a number of different varients in my albums.
They came either Flat backed or Grooved back and were made by "Jennen's & Co." See my image attached, below. It shows both designs, all with 3 lugs fitted.
Jennens front.jpg Jennens reverse.jpg
Hope this helps to clear that up
Ken (The Fatboy)
PS.
They are OSD Collar Badges