PART NO.  SPL.PAGE  DESCRIPTION                                                           
1H3275    15.F.1    Oil seal (internal late 1500 gearbox)  Com.(E)GD101 (late 1500 onward)
    -(previously 1H3339)
1H3275    16.F.1    Oil seal -rear extension -(internal, gearbox assy, 1600 and
    1600-MK-II)
1H3275    TC.F.1   Seal  Oil seal -(rear extension, gearbox assembly, Twin Cam)

A new original style seal produced with the Rover brand on it. Vintage of this piece would be sometime during reign of the Rover car company or it's successors, perhaps before sale to BMW, or at least before the successive MG-Rover Co., Ltd. (by Phoenix Group) was sold to the Chinese. Notice the external felt dust seal and the internal rubber seal with garter spring. That outer felt seal is very nice to have in a dirty environment (like under the car).

More information about this original type part, and some modern replacement type rubber lip seals, can be found in the gearbox tech article GT-111C