These models were originally designed in the early 1940’s by The Grenby Manufacturing Co.  Arter Grinding Machine Company began producing them in the early 1950’s.   These dual-purpose grinders were designed for tool room or production work where a space saving machine is needed.  It is two grinders in one.  A simple change of the wheel-heads transforms it from a plain cylindrical grinder to an internal grinder.  Unfortunately, neither The Grenby Manufacturing Co. nor Arter Grinding Machine Company kept an individual stock list of these machines.  Therefore, early additions of this model cause difficulty in identifying the correct spare part needed.  Sundstrand, Centro-Metalcut, Inc. and Tri-CAM, Inc. all manufactured new versions of this model and most spare parts are available for these models.