Authentic Corvette part top cast 7/8" (not a 1" passenger car replacement that is so often marketed as being appropriate for Corvette by shysters). Bottom cast 5462389, R8, B223 plus 2 semi circles that represents Delco trademark.

Note the rust free reservoir bowl. This was a beautiful original before the stainless sleeve by SSBC, with new internal seal kit.

Main cap has NO lettering around the perimeter on the surface. Cap includes authentic smaller cap, washer, thumb screw with machined groove for retention of cap gasket. Cap may be an anomoly, as the majority I have seen have lettering around the perimeter. (Note: I have never seen an aftermarket master cylinder for a 1963 Corvette that was faithful to the coolie hat type Corvette cap with a central thumb screw. EIS, Wagner, Rabestos all had aftermarket master cylinder that fit a 1963 Corvette, but none had a cap remotely like the collie-thumbscrew. And that's why I do not completely rule out this cap without writing in the surface is not authentic. I know how parts are manufactured and how anomolies can occur in mass production.)

Ready to bolt on unless you wish to touch up the Black paint. Truthfully, I'd replace the cap and small cap because they are not perfect, but few originals will replate flawlessly after years of exposure to corrosive brake fluid and that vapor. Shop with confidence, 100% authentic and priced accordingly.