National Geographic : 1917 Aug
Photograph from Press Illustrating Service, Inc. CHECKING AND WEIGHING SHELLS FOR THE EUROPEAN BATTLEFRONT The demands of shell manufacture are very exacting. A variance of weight of only I per cent orso isallowed. The shells have toundergo from 30 to 50 operations, varying with factories, from the time the rough forging is receiveduntil thefinished shell isturned out.