I have learned a bit about pressure gauges from Frank, who used to manufacture them, and from Stuart, who made a 5″ vertical boiler which was the inspiration for my 6″ build.
For one thing, pressure gauges become less accurate as they become hotter, so steam should not be allowed into the Bourdon tube. Which means that there should be water in the line between the steam and the gauge. That can be managed with a pig’s tail coil of copper tube, or a water reservoir, which is what I made.
For another thing, gauges have varying accuracy, and I am fortunate in having a friend who has calibration equipment, so I can obtain information about the degree of accuracy of my selection of British and Chinese gauges.
Then there is the aesthetic appearance of the gauges. A matter of taste, but I really like the older “Smiths” made in UK gauge.
So this is what I ended up installing. I might change my mind later, but for the moment…..