I've been thinking this over, and don't know the answer, however I don't recall seeing "sheaf of wheat" logo's on barrels with tube numbers as on Purdeys,Bosses, etc.. The ribs of these guns are invariably engraved with "Made of Sir Joseph Whitworth's Fluid Pressed Steel" either on the top or bottom. The tube numbers are stamped on the loop. and are mostly found on chopper lump barrels. I will keep better mental notes in the future.

All the best, Mal