There are two answers. Yes, you have the typical replacement cover that was used on many remanufactured units. Your master cylinder should also be painted black and as mentioned in about every post for 1967-70 power brake boosters, it would all be painted as a unit originally. Component painting will stand out.
Then, you have to wonder if the cylinder on your car is even an original-style Bendix or not. Easiest way is to reach underneath and feel for the center-bolt in the bottom side. Replacement cylinders usually only have the casting area, with no bolt. Then, you have the hex-head type or the allen bolt type. I think your date shoeld have the hex bolt type but others may be better to ask that detail from. I began my restoration with pretty much the same questions and same incorrect parts on my example. Most 50-year-old cars have had this item replaced 1 if not 5 times over the years.