I got knocked by a fire inspector for writing the year I installed a gauge on a customer's system (replaced a 5 year expired one) on the face plate in sharpie marker. The gauge was new but was leftover stock on my shelf after the new year. As usual (with left over gauges) I popped the cover and neatly wrote the year I installed the gauge on the face of it. I used to write it on the cover or on an "Installed Date" sticker on the cover (as Viking now supplies) but found it would get wiped off/indecipherable over time.
The inspector said he had know way of knowing if someone was lying about replacing the gauge (which honestly I've suspected cheap customers of doing) if they just changed the date on the gauge and would only accept the manufactured date (printed on the gauge itself).
I'm just wondering what other's thoughts are on this. Clearly the gauge was new (in good shape) and hadn't been beat up over the past 5 years. And IMO, NFPA is more concerned about 5 years of wear and tear on an in-service gauge (pressure changes, debris, etc.) than they are saying a gauge sitting on a shelf automatically goes bad after 5 years...