I've recently acquired a 1920 31/2 hp Sv. Partly dismantled, but coming together fast.
The correct plain timing cover is missing , years ago. It had a later replacement , the one with oil pump holes.( no oil pump with the one I've got with the bike)
Happy to buy the correct type or swop my later one for your earlier . Badge is missing on mine and I've bought a new one from the club , so hope someone can help , I believe this plain type was fitted from 1915 to 1921.