There are several variations of this chuck.  Some of them have clear marking that reads: "Millers Falls Co., Millers Falls, Mass.  Pat'd September 29, 1896", some others have no markings and their look is a bit different. 

From the study of catalogs and actual drills it appears as chuck with markings is earlier then the one without.  This would suggest that chucks without marking begun appearing after patent license expired.  If this assumption is correct then estimated date of "no marking" chuck implementation would be c. 1903 or after.

The chuck we will see here was one of the most often used on hand drills produced by Millers Falls Co.  I have seen them on No. 1, No. 2, No. 3, and No. 5 drills and their variations.  There is also difference in dimensions between chucks used on smaller drills, like No. 1, No. 3, and No. 5 and chuck used on No. 2 drill.  Chuck on No. 2 drills is larger.

The earliest implementation of this chuck I was able to find is in catalog published in 1896 by Hammacher, Schlemmer & Co. and it was installed on No. 1 and No. 2 hand drills.

Catalog "B" Pocket Edition - c.1903 shows three drills with McCoy's chuck.  All are with marking that reads:  "Millers Falls Co., Millers Falls, Mass.  Pat'd September 29, 1896".

This chuck was used for many years on various drills.  However, No. 2 drill was equipped with a new spring chuck sometime after 1900.

On the following pages I will show photographs of three variation and explore internals of these chucks.