A very elegant solution Bruce, hope you don't mind my input but I have used a few of those plastic faced gauges on various flame fired engines (including a Jensen) in recent years without any problem. I have been told it's not too difficult to replace the plastic with glass but unless there is a very major burner issue I can't see that would be necessary.
Dave
Hi Dave....as I said prior , I have made (& sold) well over 60 of these either by word , forum & eBay , as you stated...people should be ok using them on flame fired boilers...but all one has to do is look at all the absolutely filthy soot encrusted boilers on some of the flame fired Jensens listed on Ebay right now to know the flame got way out of hand, I have bought many Jensens with the whistle handle Burnt on the bottom side. I have been asked to provide a replacement lens (or the whole pressure gauge) from Ebayers who thought a bowl of gasoline... or a torch was a fine way of heating a boiler. (YES, that has happened) I also don't have "spare lenses" sitting around to supply for their errors, I get 1 complete gauge...which I disassemble to a large extent to do what I do to them. People can surely do whatever they desire with them...but please don't expect me to insure that kind of foolishness 😊