Olson's book does not contain any reference to a Type G Mauser Sporter.

His book lists data from the 1930 Mauser Co catalog as follows; Type A, Type B, Type K, Type S and Type M plus the African model, and all the Patterns of each Type that were produced as factory standard. Other features were available on special order.

The Type S and Type M carbines (19.69" barrel) were both stocked to the muzzle, the Type S having a slight schnabel finish to the end of the stock and the Type M having a steel band and end cap at the muzzle. The Type M carbine had a flat bolt handle as opposed to the Type S having the pear shaped knob.

The G preceding the serial number stamped in the barrel channel is maybe the first letter of the code word for the pattern of Mauser. For example the Type A Mauser uses W and Y as the first letter of the code words for Type A patterns, my Mauser Type A Pattern No. 1 has W stamped in the barrel channel. I do not have Jon Speed's book which has the codes for the different types and patterns (I only have a copy of the list from his book of codes for the Type A patterns and I presume he does list the codes for the other Mauser types).