I restore a lot of broadcast consoles, many of them Gates / Harris. The gray color used n the tube series of transmitters can be matched perfectly with the following: KRYLON RTA 9205 primer (it dries flat) and Rustoleum Crystal Clear # 7901. This is also a great match for Hammarlund cases like the HQ series.
See
Restorations at
www.bobmayben.com . The Gatesway was completely stripped to the metal.