Tough question, when they started in 1923 the majority of the rifles had a barrel band sling swivel attached to the stock. At the same time there were some with swivels attached to the stock only and later a barrel band swivel ahead of the forend.
I don't know when they started moving it away from the stock but seems any time period I look at I can find several types.
A picture of the rifle in question or the G&H number from the barrel might help.
Very early G&H rifles, most likley before they had numbers.
