This is the first K-Model Rear Hub. 19" Rear Rim(non drop center). Stock on 1952 and 1953 K Models (some say early '54 too) It has a weird, extra-wide double ball bearing, short spacer and cork seal on the drive side (which was used until '62 actually). If my measurements are correct, I could replace the wide bearing with 2ea thinner ball bearings (like the -54 part number hub)? I'd run the 2 bearings with the small ring spacer on the bearing IDs - and the left side has the same bearing on all years. This hub is unique since it's steel, with a larger flange on the drive-side - and a smaller flange on the left (which the spoke head hook into the hub, like a front 1/2 brake hub). The left-hand-thread bearing retainer and dust shield, is also the same part number as the 1/2 brake hub. Confused now? How about inside spokes opposite directions, outside spokes opposite directions, cross three, cross two . . . Where's my Sudoku ?