The machining and finishing of the 75 recuperator was in the hands of the Rock Island Arsenal and the Singer Manufacturing Co., which built a costly plant especially for the purpose at Elizabethport, N. J. The first recuperator of this size to appear and be accepted under the severe tests came from the arsenal in October. Thereafter the production ceased for a while. The contractors indeed built recuperators in this period, but the recuperators could not pass the tests. The machining and production of parts seemed to be as perfect as human skill could accomplish, but still the devices would not function perfectly. Adjustments, seemingly of the most microscopical and trivial sort, had to be made--there was trouble with the leather of the valves and with oil for the cylinders. These matters, which could scarcely cause any delay at all in the production of less delicate machinery, indicate the infinite care which had to be employed in the manufacture of the recuperators. At length the producers smoothed out the obstacles and learned all the secrets and necessary processes, and then the 75-millimeter recuperators began to come--2 in January, 1919, and then 13 in February, 20 in March, and 23 in April. It should be remembered that by quantity production in this particular is meant the production in quantity of recuperators of such perfect quality as to pass the inspection of the Government and to be accepted as part of our national ordnance equipment. In this inspection the Government was assisted by French engineers sent from the great artillery factories in France which had designed the recuperators and which until the successful outcome of the American attempt were their sole producers. Such inspection naturally required that the American recuperators should be the equals of their French prototypes in every respect. Because the production of French recuperators stands at the summit of American ordnance achievement, here at this point, before there is given any account of the manufacture of field artillery, the theme of this chapter, a performance table is inserted to show the records written by the various concerns engaged in making these devices. _American acceptances of recuperators by firms on Army ordnance orders only._