For sale is a 8" diameter Ashton steam gauge. This gauge includes a double spring mechanism. While this gauge is used, and apparently old, it still works well. It has a regular 1/4" NPT pipe fitting.
I tested this gauge. I connected it to my compressor and it showed the exactly correct pressure. While I personally would not mount it on a compressor tank due to its weight and vibration, you can use it in any application where it is bolted to the wall.
This gauge has an assortment of very minor scratches, but no gouges, serious dings, engravings, and so on. It might seem that it is missing the glass, but in fact the glass is there. The glass on it is in great shape. Though this gauge was used, probably it lived a sheltered life inside some control room, that would be my guess. But I can only make uneducated guesses.
I purchased this gauge at Goodwill and have a receipt.
The only cleaning that I gave to this gauge was cleaning the glass with Zeiss Lens-Cloth. Nothing else.