To United States buyers of 1960 the GK designation clearly indicated a particular buttstock profile rather than a 'swept back' bolt handle.

If an American buyer of the early 1960s ordered an MC or MCA as shown in the Stoeger catalog, it came with a swept back handle.

If the same buyer preferred the stock profile of a Model 1952, they were advised to order Model GK.

A. F. Stoeger advertised as the 'sole supplier' to the U.S. of Steyr arms.

Stoeger, 1960 - "In response to popular demand we can now supply any Mannlicher Rifle or Carbine with a conventional stock as used in Europe.
There is no extra charge for this- the price that applies to desired model remains the same; merely specify "GK-Model 1952 Stock" prominently on your order. Delivery takes about 90 days."

Stoeger, 1961 - "Mechanical specifications are the same for all models (Model 1961-MCA, Model 1960-MC, and Model 1952-GK)".

None of this, of course, verifies the origin of the GK designation or what it may / may not have defined when first used. It does show an established branding by 1960 to U. S. buyers of the GK as a straight stocked rifle or carbine that is otherwise identical to Models MC and MCA.

These are, however, the same buyers who had by then come to refer to all stutzen, regardless of maker, as being 'Mannlichers' or 'Mannlicher Stocked'.