The only S&G I have come across is "Salmon and Gluckstein". Beginning as small-time cigar manufacturers in London UK, by the turn of the 20th century Salmon and Gluckstein Ltd was the world's largest retail tobacconist, owning 140 shops in 1901. Salmon and Gluckstein Ltd was bought by Imperial Tobacco in 1902 and the brand was not dropped until 1955.
Very little is known about them as pipe manufacturers, and it would be fairly safe to assume that as retail tobacconists they would have more than likely sub-contracted the manufacture of pipes to another company. However, a book was printed in London in 1899 by Salmon and Gluckstein which showed a variety of pipes that were being made and offered for sale by this company.
As I said above, the tradename "Salmon & Gluckstein Ltd" stopped in 1955, so if your pipe is a true "Salmon & Gluckstien", it has to be pre-1955.
In addition to this, which makes me think that the pipe is not a "Salmon & Gluckstein", is that the trademark for "Salmon and Gluckstein" was S&G.LD with the D being superscript and underlined, within an oval. Here is a picture of the trademark
Sorry, but that is all the info I know.