Winchester made a Model 74 in a semi auto that was sold to the Brits just before WWII that were equipped with a silencer. The Brits were expecting a German invasion and the Home Guard was issued these shooters as sniper rifles. If it's marked RAF, it could be worth a bunch of money to a Winchester collector. The silencer was made by Parker Hale.
I have never seen a 1906 22 caliber with a silencer but it wouldn't take much to fit one.