The units you've got are substantially different from either the Alden or Watson units. They are dead simple with exactly 3 moving parts, the hinged door, the round screw on cover, and the crank handle. There are no frame counters, sprockets, or anything else to complicate matters. There is nothing to break or wear out. Loading the machine is dead simple too. All bulk film is delivered with the emulsion side IN. Simply unscrew the red door, drop the roll of film (with the center core if it has one) over the spindle, thread the leading edge of the film through the felt light trap, replace the round cover, and screw it down. Everything follows the natural curve of the film. Easy!