“I admire the master ring platform, its capabilities and its 120-plus years of heritage. I believe it is simple and elegant.” invention was genius, and I believe the fullest impact of the master ring technol- ogy was not immediately appreciated. In fact, it was certainly an invention decades before its time. I have several late 19th century and early 20th century P.F. Corbin catalogs (scans, not the original texts), and the earliest direct reference to master ring that I see is in the 1905 product catalog (Figure 2). There, the company lists single shear line and master ring cylinder options avail- able for unit locks, as rim, mortise and dummy cylinders — although it’s unclear if the dummy cylinders are rim or mortise. Corbin does not specifically mention the larger cylinder diameter but does im- ply this by drawing larger cylinders to represent the master ring product. Corbin offered the common single shear line pin tumbler cylinder prior to the inclusion of the master ring-type product (and even offered these cylinders alongside flat steel key, bit key lever tumbler locks, as seen in its 1895 product catalog). The company describes the function of the master ring cylinder as follows: “In a master keyed arrangement, the Master Ring surrounds the key plug. The Change Key operates the key plug, and the Master Key oper- ates by lining up the breaks in the pins at WWW.ALOA.ORG . . - . II I, 111 #'' Keying System for Group of Hospital Buildings oO Q RESlOeNCt( OAHAOE GROUP MASTER /MEDICAL I GRAND \ ma s t e r s pe c i al \ fC LO T HING INOUSTRJAL^ M A S T E R y ^ M A S T E R J G R E A T \ GR AN D MASTER i feU SINES^ GRAND ^MASTER,/ COTTAGE SPECIAL KEYS This chart explains the key combinations for locks supplied by us for a group of hospital buildings, and illus- trates the accurate classification, the large number of segregated groups, and the ease of adaptation of our master- keyed pin-tumbler cylinder lock for complicated installations. Even this intricate lay-out could have been ex- tended without duplication or affecting the secTxrity. The regular Corbin master-keyed cylinder, with one key- way for all keys, is used. The Service Keys are indicated by the small circles. There are (1) single and (2) sets alike, but each single key or set is different from all others. The Master Keys indicated by larger circles give admission to each of the different groups of buildings and to no others. The Two Grand Master Keys enable the chiefs of the Medical and Business Corps to enter any door under their jurisdiction and no others. The Great Grand Master Key enables the head of the institution to enter any door at will. Any Key in the entire system can be fitted as a service key to a desk, a wardrobe or a padlock. The service key to the janitors’ quarters can be made to pass the janitors’ closets in all buildings; the plumbers’ key can be fitted to the shut-off cabinets as well as their apartments; the housekeepers’ room key can be made the same as that for the supply cupboard. The number of combinations is practically endless. The Special Keys are not master keyed. They fit lockers, fire boxes, etc., where individual service alone is desired. Figure 3. At the time of the master ring’s inception, master keying theory was perhaps slightly less evolved than it is today. the outer line of the Master Ring.” Corbin goes on to state that the above arrange- ment “combines in a single shell, two cyl- inders using the same keyway for both the Change Key and the Master Key.” The company very clearly marketed the master ring for use when requesting mas- ter-keyed cylinders and seemed to suggest traditional single shear-line construction for non-master-keyed requirements. This tells me the problem, or at least the threat of incidental keys was real, and given the fact that the company marketed changes as “unlimited,” it had to back that claim. This also reveals an understanding of mas- ter-keying theory as sound in its concep- tion, although perhaps slightly less evolved (Figure 3) as it stands in the 21st century. MAY 2021 KEYNOTES 37
