Found these on another member's site:
At this point, three other sets of Burmese double knives are known to me. The Metropolitan Museum, accession number
36.25.817a–c is a simple utilitarian set with plain blades and plain smooth ivory hilts. The set was sold by W. O. Oldman to George Cameron Stone before 1935, and bequeathed to the Metropolitan Museum in 1936.
The Royal Ontaria Museum has another set, under accession number
927.59.5.1. Overall form of blades and hilts are closer to ours, but here the hilts are made of brass with bone plates. 19th century. No provenance is given.
The last set is in the National Museum of Thailand. See photo by Gary Todd on
flickr.com.
See
Mandarin Mansion 'Burmese double knives for an excellent article on these knives.
Somewhat Rare, but they do exist.