The NASG (Nat'l Assoc. of S gaugers) has a really nice website that has about as complete a listing of everything done in S-gauge as anyone (I suppose one could check it against Greenberg's pocket guide...). Here's their page for the 300: http://www.nasg.org/SProductGa...ltype/index4-4-2.php and it appears that what you have is the middle loco shown in the picture - indeed from 1946 or possibly 1947 as Tom said. David Doyle's book - 'Standard Catalog of American Flyer Trains' sez that with the flat sheet-metal tender sides, its the second of six variations of the #300 - produced in 1946 and into 1947. The first variant, produced early in 1946, had indentations on the sides of the tender where "Reading" was stamped.