Picked up this gauge cluster at a swap today. Heavy cast aluminum with a Moon plate on it that may have been added. Any thoughts on origins?
At one time I considered adding a three gauge Moon panel that consisted of Water Temperature, Oil Pressure and Voltmeter. Each of the gauges had the mooneye's on each gauge face not on the panel itself.. The 4 gauge panel you bought looks fine to me but not sure its of Moon manufacture. The gauge metal on your 4 gauge panel appears to be a lot thicker then the present panel they are selling.
Like everything else, they don't make them like they used to. That 4 gauge panel looks quite substantial. I once made the mistake of buying a Moon 8K Tach the one they are still selling. It was a plastic POS made in China by small children. Fortunately I got rid of it on the auction site.
Moon still sells 2, 3, and 4 gauge panels just like that except they don't have the tag on them, but the panels are actually made by Offenhauser and sold as Moon. You can find 'em at Summit as Offenhauser branded.