I've found a batch of NOS Universal 16mm stainless steel buckles. Rather than the more common "U" buckle, these have a much more understated "Universal" engraving on the side. The seller claimed that these were nearly identical to Patek buckles, which are known to date to the early 1960s, and that the jewelry store--now out of business--where she had acquired them was once a Patek and Universal Geneve dealer in Upstate New York. I checked out the claims and believe that they're accurate, adding a charming little bit of provenance to these great buckles.
I did my homework on the Patek connection too. The last two pictures (below) are from the net, showing the identical style in a Patek buckle. Based on my research, I believe that this very unique and particular buckle style was commissioned by the Henri Stern Watch Agency of New York City, who was then the only authorized Patek and Universal Geneve importer and distributor in the United States. The Patek examples I found were cast in white gold, while my stock of Universal Geneve buckles is all in steel.
These fit any watch strap that tapers down to 16mm on the buckle side. They are easily installed using a common spring bar tool or, in a pinch, a toothpick.
Allow me to suggest a Horween Shell Cordovan Leather Strap with one of these buckles as the perfect, elegant way to finish off your vintage Universal. If you need a hard-to-find 19mm strap, like so many different Universal references require, I've got those covered here.
Price: $200 USD, shipped, in the US. International orders are warmly welcome, but please be in touch for a shipping quote.
Payment via check, wire, courier, homing pigeon, however you're comfortable (references are available). Paypal's fine too, but add 4% please.