Thanks, everyone!
Roger, the Mechanical CV with the swing-peg coupler (or drawbar, as the case may be) was only made in 1935. Marx got into the toy train business in 1934 with the purchase of Joy Line, and spent '34 liquidating, adapting and transitioning those trains into Marx products. 1935 was the first year of production for the windup CV. Although Marx initially used Joy Line couplers on its rolling stock, they quickly converted from the Joy Line couplers to the more familiar slot & tab by 1936. With the conversion to slot & tab, the swing-peg was obsolete so all later CV's came with a slot & tab coupler riveted to the cab floor. Another first-year quirk is the wheel mounted governor, as all later Marx windups had the governor located inside the motor, with gears driving it so it spins faster than the wheels, making it MUCH more effective! This is the best (slowest) running swing-peg, wheel-governor CV I have... glad to have this set of cars to go with it.