Mario, Your machine does have a Class "M" upper works.? There were roughly 10,000 of these upper works made (I've seen 3-digit examples), so that puts yours into about the middle period of production.? Keep in mind that the manufacture of Class "M" works of that period ceased in July 1890.? More precise dating is virtually impossible.? Many Class "M" upper works (such as yours) were "recycled" years later by individual owners and various firms who had inventory on hand.? Your example appears to have been converted to a "Spring Motor" by the original owner (not the factory) around 1900.? Your motor is not an early example of the "Triton," so evidently the original owner of your Class "M" upper works was in no particular hurry to convert it to spring motor operation.? The serial number of the motor (stamped into the front edge of the motor frame) is as important as the number of the upper works - - but neither is particularly informative! Happy New Year - - George Paul ________________________________________________________________________ More new features than ever. Check out the new AOL Mail ! - http://webmail.aol.com