Some years ago, I had the local bearing house gurus translate the seal I.D. and O.D. into a usable set of numbers and they are as follows.
National--471264-- .625 ID X 1.25 OD X .250 thick.
National--470954-- .750 ID X 1.25 OD X .250 thick.
One of these seals is slightly thicker than the OEM seal, but it worked fine and moved the wear groove to a different spot on the shaft.
Hope this answers your question. Thanks for asking this is what the ERT does.
Gene Davis Tennille, Ga.