The sawed gun was not more than two foot long--one could carry it easily under one's coat.

There was no complete maker's name; but the printed letters P-E-N were on the fluting between the barrels, and the rest of the name had been cut off by the saw." "A big P with a flourish above it, E and N smaller ?" asked Holmes.
"Exactly." "Pennsylvania Small Arms Company--well-known American firm," said Holmes.
White Mason gazed at my friend as the little village practitioner looks at the Harley Street specialist who by a word can solve the difficulties that perplex him.
"That is very helpful, Mr.Holmes.No doubt you are right.

Wonderful! Wonderful! Do you carry the names of all the gun makers in the world in your memory ?" Holmes dismissed the subject with a wave.
"No doubt it is an American shotgun," White Mason continued.

"I seem to have read that a sawed-off shotgun is a weapon used in some parts of America.

Apart from the name upon the barrel, the idea had occurred to me.