Old Money is a difficult term for something very simple: clothes that don't try too hard. Good fabrics. Clean cuts. Few colours. Things that get better with use.
A belt fits perfectly into this logic. It shouldn't shine, scream, or take over the look. It should connect.
A polo belt can work in this style if it remains understated. Dark leather, clear embroidery, solid buckle. The Ascot is the most obvious model for this. The Wellington, if the contrast can be stronger.
The key is the environment: chinos, Oxford shirt, linen shirt, knitwear, loafers. Not a costume. Just a few good things, worn correctly.
