I'm a gauge engineer for Ashcroft Inc, and restore these all the time. It appears as thought you had the bourdon tube/movement assy bright dipped in nitric acid. The only concern here is degradation of the bronze hairspring. Hope it's OK. I would suggest lubricating the gearing interface, and journal points of the movement with a light silicone based fluid. This will extend the life of the movement, and add a little resistance to any vibration or pulsation effects on application. As for the brass case/ring, I always buff them to a high luster. Spraying with a non-yellowing clear acrylic is also recommended. Calibration of these is a little tricky. You have to adjust for both span (0 to full scale accuracy), as well as linerarity (points in between).
The amazing thing about pressure gauge design is that it hasn't really changed since Mr. Ashcroft issued the first US patent back in 1852.

As an aside, we offer free restoration to any Ashcroft pressure gauge. Contact Ashcroft Inc, Stratford Ct (203) 385-0474