New old stock original Swiss made gold plaque buckles for vintage Omega watches.
You can best see the authenticity in the photos where next to the NOS Omega Geneve watch produce in 1969 and which has an authentic strap and buckle. The width of the buckle where the strap enters is 16mm. The width of the strap that fits on this buckle at the connection with the watch is 18mm.
The price for a piece is 45 euro.