Does anyone here know when the "X" was first required in reporting marks on privately owned American freight cars? Using the Clover House catalogue as a guide, I see it in use as early as 1908 (Evansville Packing Company - E.P.X. 54) and not used as late as 1933 (Union Refrigerator Transit Company - U.R.T.Co. 90158). Was it optional for that many years?
MacIndoe