Original style (3H576) as shown for the early radiator and 4-cylinder block
Later design (602915) which is on the near-side of my V8 block, shown open. This seems to have a tapered thread and does not need the crushable washer that the late plug uses. Incidentally it has a conventional right-hand thread to screw into the block, but a left-hand thread on the tap part so that when 'turning to the left to open' as for a conventional tap the spindle goes down into the body to open the valve at its base.
The off-side uses plug 53K2853 ...
... with crushable washer 6K638 as there is no room for the tap under the exhaust manifold.
4-cylinder drain point, with the later plug