TIME AND INSTANTANEOUS DIAPHRAGM SHUTTER - MODEL OF 1888
Bausch & Lomb Optical Company, Rochester, New York 1888 - 1889
Historically significant as Bausch & Lomb's first commercially manufactured shutter, the Time and Instantaneous Diaphragm Shutter - Model of 1888 marked the beginning of their Diaphragm series.
A "Diaphragm and Shutter for Photographic and Other Lenses" per the patent's title, its design was patented May 15, 1888 by Edward Bausch, Patent No. 382,858. Advertised as the "Time and Instantaneous Diaphragm Shutter", it's designated here as the Model of 1888 based on the patent, its believed year of introduction and to distinguish it from the Model of 1889. Ads for the shutter with engravings reflecting this first model, appear as early as 1890 in The International Annual Anthony's Photographic Bulletin. The engraving apparently wasn't updated for 1890, as in 1889, the Time and Instantaneous Diaphragm Shutter - Model of 1889 was already being advertised with its correct engraving.
Source: U.S. Patent and Trademark Office
The shutter's most prominent feature is its unique aperture dial bearing the "Patented May 15, '88" inscription. It's further characterized by its pneumatic release valve at the rear (on the side opposite that of the successor Model of 1889), and the lack of a retardant valve. The time of the exposure being set with a spring-tensioned lever located at the rear behind the dial. The lever is advanced, stopping at one of four detent holes for each tension level. The aperture is set by sliding and securing the linkage arm within the slot on the front dial. This adjustment increases or decreases the shutter's opening when tripped. Time or instantaneous exposures were accomplished via a selector lever on the backside. Neither the tension nor aperture settings were numerically marked, and two known examples bear no visible serial numbers. It's believed that visible serial numbers appeared, starting with the Model of 1889. The casing is marked "Bausch & Lomb Optical Co., Rochester, N.Y. & New York".
Bausch's Patent was applied for on December 24, 1887, and it's not known whether the shutter was being manufactured prior to the patent's issuance. Per Dr. Rudolf Kingslake, Bausch & Lomb began the manufacture of shutters in 1888. No advertisements earlier than 1889 have been found by me.
The Model of 1888 is the second rarest of the four known models (and/or prototypes) of Bausch & Lomb's Diaphragm shutters. Manufactured for maybe a year or less, very few examples exist.
Ad from The International Annual Anthony's Photographic Bulletin 1890