When we machine parts with various types of plating we check with our plater to allow for the plating build up. You may want to send the gage to the plater with the parts and tell him to alloy for it. This can be a problem if you are plating to a Military spec because the plater is required to apply a specified thickness so you must allow for it.
Also some parts are hard to gage after plating because they are dry. Add light oil to gage b4 using.
Hello, gauge dimensions for coated part threads are based on gauge maker tolerances along with the coating thickness of the part. I carry a line of thread gauging call Northern Gauge in Canada; perhaps I can help supply you a gauge for your specific application.