No doubt Lionel's operating milk car was a best seller post war due to a number of reasons including the ability to remotely operate something with alot of action and even a cuteness that won "mom's approval". But dont forget that moving milk via the railroad was still fresh (no pun intended) on alot of people's mind in the 40s, 50s and as far as the Boston market is concerned into the late 60s. In the New England states during the postwar period as an example, milk was moved from upstate NY, VT, and Maine creameries to producers/bottlers in CT, MA (Worcester and Boston) and Providence RI as well as NY city such as Bordens, Whiting, Hood and General Ice Cream plants primarily via the Rutland, B&M, MEC, NYNH. This included milk tank "refrigerators" such as Lionels GPEX cars, can cars similar to Lionel's operating cars, "butter dish" cars and tank-on-flat car types that would have been continually passing thru alot of towns. Milk from VT to Providence RI for example would have traveled via the Rutland and B&M to Boston, back hauled to Ayer MA on the B&M then to Worcester, MA., then transferred to the New Haven and sent to Providence either on a thru freight or local passenger (per consist and photo documentation) on the Providence and Worcester branch. Even cream (called "Western Cream" by the railroads) was transported into New England from creameries in WI and MI, most likely for ice cream production. Footnote: Credit for alot of this information goes to an acquaintance of mine, Mr. J. Horvath.