In 1857 Enos G. Allen was granted a pair of patents for steam gauges. The first of these patents was for the use of a corrugated metal diaphragm, which was a significant innovation in steam pressure gauges. The second patent introduced the use of a tapered volute spring which provided a linear pressure reading based upon the movement of the diaphragm as pressure varied. This was also an important innovation and was subject to litigation in which the National Steam Gauge Co. ultimately prevailed.

By the end of 1857 the National Steam Gauge Co. of Boston had been incorporated with Allen as superintendent, and by 1858 they were manufacturing Allen patent steam gauges. Several more patented improvements followed.

In 1860 it was announced that the National Steam Gauge Co. was merging with the American Steam Gauge Co.; in actuality it was a buy-out of National by American, and afterwards the Allen patent National gauges were manufactured by the American Steam Gauge Co.

Information Sources

• March 1858 Hunt's Merchants' Magazine and Commercial Review, page 379, in a list of 1857 incorporations: "National Steam Gauge Co., Boston / (capital stock) $40,000 / (no. of shares taken) Not stated / (par value of shares) $100 / (capital paid in) $15,000".
• 1860 Damrell & Moore and George Coolidge's Boston Almanac, page 224, lists in the category of Steam & Water Gauges, "National Steam Gauge Co., 31 Devonshire".
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• 1860-02-02 Scientific American carried an announcement that the National and American Steam Gage (sic.) Companies were consolidating, and that henceforth the National gauges made under the patents of E. G. Allen would be made by American Steam Gage Company.
• See patents 16,428 and 18,526; the datamp.org description of the latter patent provides some background on litigation involving that patent.
• We have seen a photo of a steam gauge marked "E. G. Allen's Steam Guage / Patented Jan. 17, 1860" (misspelling in the original) on the front face. We do not know who actually made this gauge.