If your car is a manual brakes drum brake car, that MC is correct.
That may be the original part for your car in which case it would be nice have restored back on your car. Especially if you are trying to do a OE resto with correct date codes and such.
But those master cylinders aren't that rare, were used on most drum brake Mopars from 67-70, so not hard to find a rebuilt correct one.
If you want to have yours restored, I recommend Brake and Equipment Warehouse in Minneapolis. New correct repro caps are available for around $75, from PG Classics and other sources of repro parts.